JPH09146141A - Automatic exposure time controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute more accurate exposure by improving automatic exposure arithmetic operation of the luminance in the vicinity of a γ conversion point. SOLUTION: In this automatic exposure time controller; a subject luminance information detection part 1 outputs subject luminance information, and an exposure area judgement part 2 judges whether shutter waveform in accordance with the subject luminance information is within a 1st area or a 2nd area. A triangular area shutter time calculation part 3 obtains shutter time at which appropriate exposure is attained by using the shutter time calculating expression of a trianglular area in the case the shutter waveform is within the 1st area, a trapezoidal area shutter time calculation part 4 obtains the shutter time at which the appropriate exposure is attained by using the shutter time calculating expression of a trapezoidal area in the case the shutter waveform is within the 2nd area, and a shutter time control part 5 controls the shutter time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic exposure time control device which is used in an image pickup device such as a camera and calculates an exposure time in exposure control of the camera or the like.

[0002]

2. Description of the Related Art Conventionally, various proposals have been made for a technique for obtaining an exposure time of a plunger shutter. However, as a product which has already been commercialized, a high-luminance side based on a γ conversion point of a camera shutter waveform is used. There is a technology to calculate the second separately from the low brightness side.

This is because it is difficult to control the movement of the plunger shutter at an intended speed, and therefore the movement of the shutter is classified into tendency for each shutter time so that the shutter time can be easily obtained.

Here, FIG. 8 is a diagram showing the movement of the shutter of the above technique in terms of the amount of light entering from the opening sector. The horizontal axis represents time, and the vertical axis represents the amount of light entering from the opening sector. ing. As shown in the figure, when the shutter blades that make up the shutter start moving and external light enters,
Since the amount of light increases, a gentle rising curve is drawn from t0 to t1. If you expose it for a long time, you can take an overexposed picture, so close the blades at the timing that matches the brightness, but if the external light is high brightness, close the shutter before the time tb elapses. As it starts, a triangle like the one in the figure is shown.

When the shutter speed is such that the blade is closed from the beginning of opening of the blade to the time t1, the graph shows a triangle and is called a triangular area. Further, when the shutter closing time after the time t1 is the blade closing time, a trapezoid is shown on the graph, so that it is called a trapezoid region. Normally, the TV value is (EV-
AV), which is an expression when the shutter speed becomes a trapezoidal region. When the shutter speed is in the triangular region, the TV value must be obtained in consideration of the opening timing of the blade.

The blade opening curve of the plunger shutter can be approximated by an exponential expression. Now, assuming that the f-number change until the shutter is opened is FN and the time is t, it is possible to obtain the f-number that changes by (1 / FN ² ) = a × t ^b (1) from t0 to t1.

In general, the AV value is obtained as AV = log ₂ FN ² (2), and the TV value is expressed as TV = log ₂ (1 / t) =-log ₂ t (3) be able to.

If both sides of the equation (1) are logarithm of ₂ , log ₂ (1 / FN ² ) = log ₂ a × t ^b −log ₂ FN ² = log ₂ a + blog ₂ t (4) . That is, the exposure amount in the triangular area is obtained by integrating the above equation (1),

[0009]

(Equation 1) Becomes

Since the EV value is represented by EV = -log ₂ S, substituting this into the above equation (5), EV = -log ₂ {(a / (b + 1)) t ^{(b + 1 )} } = − Log ₂ a + log ₂ (b + 1) − (b + 1) log ₂ t, further substituting the equation (3), EV = −log ₂ a + log ₂ (b + 1) + (b + 1) TV (6) It is expressed by a formula, thus EV, T in the triangular region
A relational expression of V and AV is required.

The EV value, AV value, and
If the TV values are EVo, AVO, and TVo, respectively, γ
EVO transformation _{point, EVo = -log 2 a + log} 2 (b + 1) + (b + 1) TVo ... a (7).

Then, if the above equation (7) is subtracted from the above equation (6), then EV-EVo = (b + 1) (TV-TVo).

From this equation, the TV value in the triangular area is TV = TVo + (1 / (b + 1)) (EV-EVo) (8).

Further, by converting the above equation (7) of EVo, EVo = -log ₂ a-blog ₂ t + log ₂ t ^-1-
It becomes log ₂ (b + 1) ⁻¹ .

Further, Avo of the above formula (2) is f when opened.
If the number is FNo, then AVo = log ₂ FNo ² .

Further, when the above equation (1) is expressed by FNo, (1 / FNo ² ) = a · t 1 ^b , and when both sides are logarithm of ₂ , log ₂ FNo ² = −log ₂ a · t 1 ^b .

That is, AVo = -log ₂ a-blog ₂ t (9)

By substituting this equation, EVo = AVo + TVo-log ₂ (1 / b + 1) ^−1. Therefore, the above equation (8) can be expressed as TV = TVo + (1 / (b + 1)) (EV-AVo-TVo + log It can be calculated by ₂ (1 / (b + 1)).

Further, at the time of second, the above equation (3) is modified and expressed by the equation: t = 2- ^TV (10). On the other hand, in the trapezoidal area, the exposure dose is
Since it is the sum of the triangular area up to t1 and the exposure amount from t1 to the subsequent time t,

[0020]

(Equation 2) It is.

When this is modified, S = at1 ^b (t- (b / (b + 1)) t1) and EV = -log ₂ S, so EV = -log ₂ at1 ^b -log ₂ (t -(B / (b + 1)) t1) ... (11)

When the above expression (11) is expressed using the above expression (9), EV = AVo-log ₂ (t- (b / (b + 1)) t 1
), The EV of the trapezoidal area is generally TV = −log ₂ (t− (b / (b + 1)) t 1) ... (12) because EV = TV + AVo.

When this equation is modified, the shutter speed t is represented by t = 2- ^TV + (b / (b + 1)) t1 (13).

From the above, the shutter speed calculation formula is: TV = TVo + (1 / (b + 1)) × (EV-AVo-TVo + log ₂ (1 / (b + 1)) (14) t = 2 in the triangular area. ^-TV (10) In the trapezoidal area, it can be calculated by TV = EV-AVo t = 2 ^-TV + (b / (b + 1)) t1 (13).

[0025]

However, as described above, in the algorithm of the automatic exposure calculation according to the above technique, the above-mentioned triangular area and the trapezoidal area are used to obtain completely different seconds. The shutter waveform in the vicinity of the γ conversion point in the trapezoidal region, which takes a little longer time, actually has a shape close to a triangular waveform, and therefore does not apply to the arithmetic expression in the trapezoidal region.

That is, the exposure accuracy of the γ conversion point becomes poor,
If the accuracy is forcibly improved, the brightness other than the brightness at the γ conversion point is affected, and the balance of the exposure accuracy at each brightness is lost.

The present invention has been made in view of the above problems. An object of the present invention is to improve the automatic exposure calculation of the brightness in the vicinity of the γ conversion point, which is a problem, and to make more accurate exposure. It is to provide a time control device.

[0028]

In order to achieve the above object, an automatic exposure time control device according to a first aspect of the present invention comprises a subject brightness detecting means for outputting subject brightness information,
Exposure area determining means for determining whether the shutter waveform according to the subject brightness information is in the first area or the second area; and a triangular area when the shutter waveform is the first area. It is appropriate to use the triangular area time calculation means for obtaining the shutter time for proper exposure using the second time calculation expression and the trapezoidal area time calculation expression when the shutter waveform is the second area. The present invention is characterized by comprising trapezoidal region time calculation means for obtaining the shutter time for exposure and time control means for controlling the shutter time.

In the automatic exposure time control device according to the second aspect, the aperture waveform detecting means for detecting the relationship between the aperture diameter of the shutter of the camera and the exposure time, and the aperture diameter detecting means for determining the aperture diameter as time. A second switching time for switching the formula of the exposure calculation of the camera is calculated according to the outputs of the first switching time determination means for determining the first time which is constant regardless of the above, and the output of the first switching time determination means. And a storage unit for storing a value based on the output of the second switching time determination unit in a memory in the camera.

Further, the automatic exposure time control device according to the third aspect is characterized in that the second switching time is set longer than the first switching time. here,
The first to third aspects have the following effects.

That is, in the automatic exposure time control device according to the first aspect, the subject brightness information detecting means outputs the subject brightness information, and the exposure area determining means outputs the shutter waveform according to the subject brightness information within the first area. In the second
If the shutter waveform is in the first area, the triangular area time calculation means uses the triangular area time calculation formula to obtain the shutter time for proper exposure. When the shutter waveform is in the second region, the trapezoidal-second calculating unit obtains the shutter-second for the proper exposure by using the trapezoidal-second calculating formula, and the second-time controlling unit calculates the shutter-second. Is controlled.

In the automatic exposure time control device according to the second aspect, the relationship between the opening diameter of the camera shutter and the exposure time is detected by the opening waveform detecting means, and the opening waveform detecting means is detected by the first switching time determining means. Means for determining the first time during which the opening diameter is constant regardless of time, and second switching time determination means for switching the expression for calculating the exposure of the camera according to the output of the first switching time determination means. The second switching time is calculated, and the storage means stores the value based on the output of the second switching time determination means in the memory in the camera. Further, in the automatic exposure time control device according to the third aspect, the second switching time is set longer than the first switching time.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of an automatic exposure time control device of the present invention. In the figure, the subject brightness information detecting section 1 outputs the subject brightness information, and the exposure area determining section 2
Determines whether the shutter waveform according to the subject brightness information is in the first area or the second area. When the shutter waveform is in the first region, the triangular region time calculation unit 3 uses the triangular region time calculation formula to determine the shutter time for proper exposure, and the trapezoidal time calculation unit 4 calculates the shutter time. When the waveform is in the second region, the shutter speed that provides the proper exposure is obtained using the time calculation formula for the trapezoidal region, and the second control unit 5 controls the shutter time.

Next, FIG. 2 shows the structure of a camera using the automatic exposure control device according to the first embodiment of the present invention, and will be described. The figure shows only the features of the present invention. In the figure, a CPU 11 which controls the whole is connected to an interface IC (hereinafter abbreviated as IF-IC) 12 via a main path, and further connected to an EEPROM 13 and an external connection terminal via a serial path. Has been done. The CPU 11 is further provided with a release switch 15 and a D switch.
X switch is connected.

A photometric sensor 17 is connected to the IF-IC 12, and a drive mechanism 19 for film winding, a plunger 20, and a shutter drive mechanism 21 are further connected via a motor 18.

The operation of the first embodiment will be described below with reference to the flowchart of FIG. When the camera is charged with a battery, the power is reset and the CPU 11 is activated to start the operation based on the program. First, the CPU 11
Performs initial settings such as setting of each port and activation of the IF-IC 12 (step S1). Subsequently, the CPU 11 reads out data necessary for controlling the CPU 11, which is stored in the EEPROM 13 via the external connection terminal 14 in advance and stores it in the RAM area of the CPU (step S).
2).

Subsequently, the CPU 11 determines whether or not the release switch 15 has been turned on (step S3).
Here, when the release switch 15 is OFF, the determination is continued, but when it is ON, the process proceeds to step S4.

Subsequently, the release sequence is executed (steps S4 to S8). That is, the CPU 11 uses the DX
I of film depending on whether switch 16 is turned on
The SO sensitivity is read (step S4). When the NONDX film or the film is not loaded, the photometry is performed as ISO100 (step S5).

Here, when the CPU 11 transfers a signal for photometry to the IF-IC 12, the photometry circuit inside the IF-IC 12 is activated, and the range monitored by the photometry sensor 17 connected to the IF-IC 12 is measured. . The photometric data is stored in the CPU 11 via the IF-IC 12. Further, the photometric sensor 17 may be divided into a plurality of parts, and can be recognized by finely dividing the brightness of the center of the subject and the brightness of the periphery.

In step S5, the brightness value is determined by CPU1.
When it is input to 1, the CPU 11 subsequently performs the AE calculation (step S6). This will be described in detail later, but here, the exposure time TSHUT for controlling the shutter drive mechanism 18 according to the measured brightness to expose the film.
Ask for. The control program for actually driving the shutter drive mechanism 18 is executed in the next step S7.

The movement of the shutter will be described with reference to the time chart of FIG. The shutter blade (not shown) and the plunger 20 are connected via the shutter drive mechanism 21, and the movement of the iron needle of the plunger 20 is quickly transmitted to the shutter blade. The shutter blade opens according to the amount. When the plunger 20 is turned on via the IF-IC 12, the timer of the exposure time TSHUT starts counting. Then, the shutter blades start moving, but there is a delay of time ta before the shutter blades start opening.

After that, the shutter blades continue to open, and after the time tb has elapsed, the shutter blades are fully opened. Exposure time T
When SHUT is short, the plunger 20
Is turned off and the shutter blades are closed. When the shutter speed is long, the plunger 20 continues to be turned on even when the shutter blade is fully opened, and the plunger 20 is turned off after the exposure time TSHUT has elapsed.
I do. As there was a delay in opening the shutter blades,
Even when the shutter blade is closed, it takes time t for the movement of the shutter blade.
There is a delay of d minutes, after which the shutter blades
Close later.

The exposure control is completed by the above operation, and the CPU 11 winds up one frame to take a picture for the next frame (step S8). Subsequently, the CPU 11 controls the motor 1
The film winding drive mechanism 19 is driven by 8 to wind up the film (step S9). With the above, the release sequence ends, and one frame shooting is completed. The operation of the program shifts to step S3, and waits for the next input by the release switch 5.

Next, referring to the flowchart of FIG. 5, the subroutine "AE calculation" executed in step S6 is executed.
Will be described. First, the CPU 11 sets the previously stored photometric data as the BV value (step S11).
At this time, if the photometric sensor 17 is divided into the central portion and the peripheral portion, the central BV (BVSP) and the peripheral BV
(BVAN) is compared to perform backlight determination, or the central brightness is emphasized to match the central brightness. Therefore, if BV = 0.7 × BVSP + 0.3 × BVAN, and BVSP is multiplied by the specific gravity to obtain BV, The exposure will be suitable for the photo. Next, the CPU 11
The DX code of the previously read film is converted into an SV value (step S12). Then, the CPU 11 uses the BV
The EV value is obtained from the value and the SV value (step S13).

Subsequently, the CPU 11 determines the exposed area (step S14). AVo + TVo−log ₂ (1 / (b + 1)) −lo corresponding to the γ conversion point brightness EV0
g ₂ (1 / (b + 1)) is a RAM name of P1 and is preset in the EEPROM 13 as a correction value for the triangular area. Further, it has an offset amount P3 of the γ conversion point, which is also set in the EEPROM 13.

Then, as shown in FIG. 6, the γ conversion point is arithmetically shifted to the γ conversion point. That is, the EVo-P3 is used as the γ conversion point in the calculation, and is compared with the EV value that is the input brightness. That is, EV <EVo-P3 = AVo + TVo-P
It is determined whether it is 1-P3. In this decision,
The side slightly lower than the γ conversion point brightness EVo is judged as a triangular area. With this, the trapezoidal waveform that is closer to the trapezoidal region than the γ conversion point and actually shows a waveform close to the triangular region waveform is also calculated with the equation for the triangular region, and the seconds are calculated. The balance of

If it is determined in step S14 that the brightness is high, the area is a triangular area, so γ that matches the shutter waveform is used.
The conversion point brightness EVo, that is, AVo + TVo-P1 is used to obtain the second in the triangular area (step S15). Next, the exposure time TSHU is calculated from the TV value calculated in step S15.
T is calculated (step S16). The smaller the shutter waveform is, the larger the error in calculation becomes, so that the high-brightness adjustment parameter EETRG is provided. Therefore, EET
The RG has a constant set in the EEPROM 13 so as to ensure the accuracy of the maximum brightness in the automatic exposure interlocking range of the camera.

That is, the exposure time TSHUT is obtained by TSHUT = 2- ^TV + EETRG, and the AE calculation is completed.

On the other hand, when it is determined from the determination in step S14 that the luminance is lower than the calculated γ conversion point,
A TV value is calculated (step S17). The equation for obtaining the second in the trapezoidal region is the above equation (13), but (b / b + 1) t
1 is a correction value for correcting the high-luminance side in the trapezoidal area, and is stored in the EEPROM 13 as a RAM name P2. Then, in step S18, the exposure time is obtained from TSHUT = 2- ^TV + P2, and the AE calculation is ended.

Next, FIG. 7 shows the structure of an automatic exposure time control device according to a second embodiment of the present invention, and will be described. In the figure, in the camera 100, switching is performed by the opening operation of the shutter 107 and the opening operation to control the light amount of the light incident from the taking lens 108 and adjust the exposure amount on the film (not shown). The shutter 107 is controlled by a lens shutter control unit 106 including an actuator and a driver circuit. Lens shutter control unit 10
Reference numeral 6 denotes a light receiving element 111 arranged at a position corresponding to the film surface, which is controlled by the sequence controller 113 of the adjuster 110 at the time of adjustment and is controlled by the second time control unit 105, and a processing circuit for the output thereof. The relationship between the time when the shutter 107 is fully opened and the diaphragm can be detected by the aperture waveform detector 112.

The shutters 107 are opened one by one differently depending on the performance of the lens shutter controller 106 and the like. Therefore, in the camera production process,
Such aperture waveform detection is required.

The area switching data calculation unit 114 determines the above-mentioned triangular area and trapezoidal area from the detection result of the opening waveform, and from the switching point, that is, the first switching point, the switching point, such as second calculation, that is, the second. For calculating the switching point of, and is configured by, for example, a personal computer or the like.

The second switching point data thus obtained is input to the memory section 102 such as an E ² PROM provided inside the camera, and the exposure area determination section 103 refers to this data at the time of photographing by the camera, Switch the calculation method for seconds. The second time calculation unit 104 performs the second time calculation, and the second time control unit 105 controls the shutter via the lens shutter control unit 106 at the time of shooting according to the second time data thus obtained.

Hereinafter, FIG. 7B shows a flow chart showing the operation of the second embodiment, and FIG. 7C shows the second operation.
The state of the adjustment process using the embodiment of FIG. FIG.
In (c), reference numeral 120 is a worker, and reference numeral 11
Reference numeral 5 is a reference light source, reference numeral 111 is a light receiving portion, and reference numeral 110 is a personal computer in charge of an input calculation portion of the adjuster.

Each camera 100 is set in the present invention by the operator 120 at the time of production.
When 10 is operated, as shown in FIG. 8 (b), the opening waveform is detected, the time t related to the triangle / trapezoid switching point is calculated, T0 is calculated from this t, and it is input to the storage section (step S21 to S24). In this way, the personal computer 110 calculates the data for correcting the variation in the shutter operation of the camera, and the personal computer 110 calculates the data.
02.

[0056]

As described in detail above, according to the present invention,
It is possible to provide an automatic exposure time control device that improves the automatic exposure calculation of the brightness near the γ conversion point, which is a problem, and performs more accurate exposure.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an automatic exposure time control device of the present invention.

FIG. 2 is a diagram showing a configuration of a camera using the automatic exposure control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing an operation of the first embodiment.

FIG. 4 is a time chart for explaining the operation of the shutter according to the first embodiment.

5 is a flowchart showing a sequence of a subroutine "AE calculation" executed in step S6 of FIG.

FIG. 6 is a time chart showing how the γ conversion point is arithmetically shifted to the γ conversion point.

FIG. 7 is a diagram showing a configuration of an automatic exposure time control device according to a second embodiment.

FIG. 8 is a diagram showing the movement of a shutter in the related art, converted into the amount of light entering from an aperture sector.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Subject brightness | luminance detection part, 2 ... Exposure area determination part, 3 ... Triangular area time calculation part, 4 ... Trapezoid area time calculation part, 5 ... Second time control part.

Claims (3)

[Claims] 1. A subject brightness detecting means for outputting subject brightness information, and an exposure area determining means for determining whether a shutter waveform according to the subject brightness information is in a first area or a second area. And, when the shutter waveform is in the first area, a triangular area time calculation means for obtaining the shutter time for proper exposure by using the time calculation formula in the triangular area, and the shutter waveform is in the second area. In the case of, a trapezoidal area time calculating means for obtaining a shutter time for proper exposure using the trapezoidal area time calculating formula, and a second time controlling means for controlling the shutter time are provided. Characteristic automatic exposure time control device. 2. An aperture waveform detecting means for detecting a relationship between an aperture diameter of a shutter of a camera and an exposure time, and the aperture waveform detecting means determines a first time when the aperture diameter is constant regardless of time. A first switching time determining means, a second switching time determining means for calculating a second switching time for switching the expression for calculating the exposure of the camera in accordance with the output of the first switching time determining means; 2. An automatic exposure time control device comprising: a storage unit that stores a value based on the output of the switching time determination unit 2 in the memory in the camera. 3. The automatic exposure time control device according to claim 2, wherein the second switching time is set longer than the first switching time.