JPH0348568Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to an aperture control device for a camera.

(Prior art) For example, in a single-lens reflex camera equipped with a programmable automatic exposure control device, when the camera is released, the aperture lever is moved to narrow down the aperture aperture, and when the aperture lever moves to a position that corresponds to the appropriate aperture aperture, the aperture lever is moved as the camera is released. It has an aperture control device that detects this and stops the movement of the aperture lever.

Conventional aperture control devices for color cameras include a position control system that detects the position of the aperture lever itself and controls the aperture lever based on this position signal, and a time control system that controls the aperture lever based on time. There was a problem due to this. The position control method described above has the advantage that even if the moving speed of the aperture lever changes, no aperture error occurs due to the change in the moving speed, as shown by a, b, and c in Fig. 1. However, if high-precision aperture control is to be performed, a high-resolution aperture detection means is required, which requires a complex and highly accurate electric circuit, which raises the problem of increased production costs. Additionally, while a relatively simple electrical circuit is sufficient for time-controlled devices,
The problem is that if there is variation in the speed of the aperture lever, this will directly appear as an error in the aperture opening. Figure 2 shows this. When the aperture changes at a predetermined speed as shown by x in the figure, accurate aperture control is performed by time control; If the aperture speed is too fast, as shown by y in the figure, or if the aperture speed is slow, as shown by z in the figure, the speed error, in other words, the line x
An aperture error will occur by the amount of deviation from the aperture.

(Purpose) The purpose of the present invention is to make it possible to perform highly accurate aperture control with a relatively simple circuit configuration by taking advantage of the advantages of a position control type aperture control device and a time control type aperture control device. An object of the present invention is to provide an aperture control device for a camera.

(Structure) The feature of the present invention is that the position signal from the aperture lever position detection means is compared with the upper part of the stored signal of the aperture stop value storage means, and when the upper parts match, the lower part of the stored signal is compared. The aperture stop signal is output by comparing the lower part with the time signal from the timer at regular intervals, and in other words, the aperture stop signal is output based on the comparison of the lower part.In other words, the aperture stop signal is roughly controlled based on the position control method. After that,
The reason is that fine aperture control is performed using a time control method to fill in the blanks.

Hereinafter, the present invention will be explained with reference to FIGS. 3 to 5.

In FIG. 3, a microcomputer (hereinafter referred to as "microcomputer") 1 receives an aperture position signal FCAL, which is generated every time the aperture lever moves a certain amount, from an aperture lever position signal generator 2 of the camera. ing. The aperture position signal FCAL is input to the position detecting means 3 in the microcomputer 1, the position of the aperture lever is calculated based on the aperture position signal FCAL, and the calculated signal is input to the comparison means 4. The microcomputer 1 has a calculation unit 5 which calculates at what aperture aperture the aperture should be stopped depending on various conditions such as subject brightness and film sensitivity, and an aperture stop value storage unit 6 which stores the calculated aperture stop value. The aperture stop value signal stored by the storage means 6 is input to the comparison means 4. The microcomputer 1 includes a pulse generator 7 and a timer 8 that counts pulses emitted from the pulse generator 7 at a constant time interval and outputs a signal every time a constant count value is reached, and therefore at a constant time interval.
The signal from the timer 8 is input to the comparing means 4. The comparing means 4 has a control device and a counter for signal processing, and first, when the aperture lever position signal from the position detecting means 3 is input, the high-order bit of the counter is counted down and the aperture stop value storage means 6 is stored.
When the upper bits match and a borrow is output, the lower bits of the counter are counted down by the signal from the timer 8 and are stored in the aperture stop value storage means 6. It is compared with the lower bits of the signal, and when the lower bits match, an aperture stop signal is output. This aperture stop signal is applied to the aperture stop means 9, and the aperture stop means 9 controls the aperture magnet 1 provided outside the microcomputer 1 based on the input of the aperture stop signal.
The aperture magnet 10 restricts the aperture operation of the aperture mechanism and controls the aperture aperture to a desired aperture. As a mechanism for restricting the aperture operation based on the operation of the aperture magnet 10, a mechanism already known in automatic exposure control cameras can be used. The timer 8 also measures a preset time sufficient for the aperture lever to move over its entire stroke, and inputs the time to the position detecting means 3 and the comparing means 4.

FIG. 6 shows a specific example of the aperture lever position signal generating section 2 and the position detecting means 3. In Figure 6,
On the path of the brush 11 that moves downward in the figure in synchronization with the operation of the aperture lever, two comb-shaped electrodes 12 and 13 are arranged such that the comb-teeth portions of both electrodes 12 and 13 are engaged alternately. , 13 with appropriate spacing between them. The brush 11 is grounded, and the electrode 12 is connected to a DC power supply Vcc via a pull-up resistor 14 and an inverter 15.
The electrode 13 is connected to a DC power supply Vcc via a pull-up resistor 16, and is also connected to an inverter 17. Now, suppose that the brush 11 moves in synchronization with the operation of the aperture lever, and each time the brush 11 contacts the electrode 12 and the brush 11 contacts the electrode 13, a high level signal is generated from the inverter 15 and from the inverter 17. These signals are output as aperture lever position signals FCAL1 and FCAL2, respectively, and these signals are input to the comparison means 4. Above two signals FCAL
1. FCAL2 may be treated as the same series of signals. Therefore, the two electrodes 1 in the illustrated example
2 and 13 may be used as a single electrode. Further, the aperture lever position signal generating means is not limited to the above-mentioned contact type, but may be a non-contact type using a photocoupler, a magnetic sensor, etc., for example.

Next, the operation of the diaphragm control device constructed as described above will be explained with reference to the flowchart shown in FIG. Now, when the aperture lever begins to move with the release of the camera, the timer 8 starts operating at the same time, and clocks up to a preset time that is sufficient for the aperture lever to move through its entire stroke. . Before this timer times up, the comparing means 4 determines the presence or absence of the aperture lever position signal FCAL from the position detecting means 3, and detects the aperture lever position signal.
When FCAL is input, the high-order bit of the counter is counted down, and the high-order bit of this counter is compared with the high-order bit of the aperture stop value stored in the aperture stop value storage means 6.
When the upper bits compare and match and a borrow occurs, the lower bits of the counter are counted down based on a signal at a fixed short time interval from the timer 8.
The lower bit of this counter is compared with the lower bit of the aperture stop value stored in the aperture stop value storage means 6. In this way, when the lower bits are compared and match and a borrow is produced, an aperture stop signal is sent from the comparing means 4 to the aperture stop means 9, and the aperture stop means 9 drives the aperture magnet 10 based on the aperture stop signal to stop the aperture operation. to restrict the aperture to a predetermined aperture.

According to the aperture control device that operates in this way, first, rough aperture control is performed based on the aperture lever position signal, and then fine aperture control is performed using time control. Even if there is variation in the movement speed of the aperture lever, the aperture error due to the variation in the movement speed of the aperture lever is only the aperture error due to the variation in the movement speed of the aperture lever within the time interval in which the aperture lever position signal is output. There is almost no problem with the above, and high aperture accuracy can be obtained. Figure 5 shows this, where line A represents the case where the aperture lever moves at a predetermined speed, line B represents the case where the aperture lever moves faster than the predetermined speed, and line C represents the case where the aperture lever moves faster than the predetermined speed.
The figures below indicate cases in which the aperture lever moves slower than the predetermined speed, and even if there are variations in the moving speed of the aperture lever, the aperture error only occurs within the small range shown by the triangular waveform and marked with diagonal lines. I understand.

(Effects) According to the present invention, after rough aperture control is performed based on the position control method, fine aperture control is performed using the time control method to fill in the gaps, resulting in accurate aperture control with less aperture error. In addition, since the aperture control using the position control method is rough control, the control circuit can be significantly simplified compared to the case using only the conventional position control method, and the time control method Since the control circuit according to the present invention has an originally simple configuration, it is possible to provide a diaphragm control device that is simple in configuration and inexpensive while being able to perform highly accurate diaphragm control.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of an aperture control device using a conventional position control method, Fig. 2 is a characteristic diagram of an aperture control device using a conventional time control method, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is a characteristic diagram of an aperture control device using a conventional time control method. The figure is a flowchart showing the operation of the device of the present invention, FIG. 5 is a characteristic diagram of the device of the present invention, and FIG. 6 is a circuit diagram showing an example of the aperture lever position signal generator and position detection means used in the present invention. . 3... Aperture lever position detection means, 4... Comparison means,
5... Arithmetic unit, 6... Aperture stop value storage means, 8...
Timer, 9...Aperture stop means.

Claims (1)

[Scope of utility model registration request] an aperture lever position detection means that outputs a position signal every time the aperture lever moves a certain amount; an aperture stop value storage means that stores a pre-calculated aperture stop value; and a timer that outputs a signal at fixed time intervals; The position signal from the aperture lever position detection means is compared with the upper part of the signal stored in the aperture stop value storage means, and if the upper part matches, the lower part of the stored signal and the time signal from the timer are compared. Aperture control in a camera comprising a comparison means for comparing and outputting an aperture stop signal based on a comparison match of the lower part, and an aperture stop means for stopping an aperture lever based on the aperture stop signal from the comparison means. Device.