JPS63169636A - Accuracy measuring instrument for focal plane shutter - Google Patents

Abstract

PURPOSE:To accurately measure a shutter speed at all times even when the quantity of light of a light source or the sensitivity of a sensor varies by converting the reference value of a comparator to a specific level according to an input signal at the time of measurement. CONSTITUTION:The output signal of the photosensor 12 is amplified 18 and then A/D-converted 22, and the result is inputted to a CPU 24. The CPU 24 performs arithmetic with a specific range which is, for example, a half the maximum level of this input signal and its output is D/A-converted 26 and supplied as the reference value to the comparator 20. Then when a measurement is taken, the output signal of the comparator 20 is stored in the register of the CPU 24 to calculated the shutter speed. The reference value of the comparator 20 is therefore converted according to the input sensitivity at the time of the measurement, thus performing invariably accurate measuring operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an accuracy measuring device for focal plane shutters.

(Prior Art) Regarding camera shutter devices, high-speed focal plane shutters have recently appeared. Depending on whether the shutter speed at this high speed is accurate or not, the photographing conditions will fluctuate, resulting in a situation where ideal photographing conditions cannot be set.

Therefore, there is a need for an intensity measuring device that measures whether the shutter device is achieving a desired high shutter speed.

Such an accuracy measuring device is configured to include a slit plate in which the slit is formed, a photo sensor behind the slit, and a floodlight in front of the slit throat of the slit plate.

When the focal plane shutter to be measured is run in front of the slit plate, the photo sensor detects the light from the floodlight only during the first and second curtains of the shutter.

The amount of light received increases gradually from the time the second and first act reaches the slit edge until it exits the other end of the slit, and after the second act reaches the slit edge, it exits the other end of the slit. It is understood that this will gradually decrease.

Therefore, the output level from the photosensor becomes as shown in FIG.

There are a differential method and a fixed level method depending on the range in which the shutter speed is determined.

As shown in Figure 5, the differential method calculates the rate of change in the amount of light received by the photosensor between the increase/decrease regions A and B, and then calculates the time between the maximum and minimum values of the rate of change in the amount of received light curve at the shutter speed T1. shall be.

In addition, in the fixed level method, as shown in Figure 6, the maximum amount of light received by the photo sensor's light receiving aperture is fixed at a threshold level of 2, and the time T2 during which the light receiving aperture is greater than or equal to this threshold level is determined by the shutter speed. shall be.

(Problems to be Solved by the Invention) However, both the differential method and fixed level method for determining the shutter speed described above have the following problems.

In other words, the differential method has the advantage that measurement accuracy does not change significantly even if there is a change in the amount of light emitted from the projector lamp, but as the curtain speed increases, that is, the higher the speed, the rate of change in the amount of received light increases. Since the positions of the maximum and minimum values of the curve tend to deviate from the relative positions at low speeds, there is a problem that the desired accuracy is not achieved.

On the other hand, in the fixed hell type, the input signal level changes due to changes in the light source, changes in the sensitivity of the photosensor, dust on the slit surface, clouds, etc. On the other hand, since the threshold level is fixed, there is a problem in that it causes an error. Therefore, in the fixed level method, readjustment such as replacement of the photo sensor or light source is required, but the operation is complicated.

Therefore, the present invention was made to solve the various problems mentioned above, and its purpose is to solve the problem even if the light intensity of the light source or the sensitivity of the photosensor changes or if dust or the like adheres to the slit. To provide a focal plane shutter accuracy measuring instrument that can always accurately measure shutter speed.

(Summary of the Invention) In order to achieve the above object, a focal plane shutter accuracy measuring device according to the present invention is provided with a photo sensor behind the slit of a slit plate, a flood lamp in front of the slit, and a connection between the slit plate and the flood lamp. In a device that measures the accuracy of a shutter device by running a focal plane shutter between the two and detecting light incident on the photosensor, an operational amplifier that amplifies the output signal from the photosensor; A comparator and A into which the amplified signals are respectively input.
A /D converter and a signal converted into /D by the A/D converter are input, and an output signal is calculated in a predetermined range, such as 2, of the maximum level value of the input signal, and this output signal is is input to the other input terminal of the comparator as a reference value via a D/A converter, and an output signal from the comparator is input, and a CPU calculates a shutter speed etc. based on this input signal. It is characterized by automatic calibration of the threshold level using the DC level method.

(effect) Next, we will discuss the effect.

The output signal from the photosensor is amplified by an operational amplifier and input to an A/D converter. The A/D converted signal is input to the CPU, and the CPU inputs a signal calculated in a predetermined range such as 2 of the maximum level of this input signal to the input terminal of the comparator via the D/A converter.

During measurement, the output signal from the comparator is input to the CPU via a register, and the CPU calculates necessary data such as shutter speed based on this input signal.

In this way, the comparator reference value can be converted based on the input sensitivity during actual measurement, so even if foreign matter adheres to the slit or changes occur in the sensitivity of the photosensor or the light intensity of the floodlight, the change will not occur. Since the measurement is performed based on the reference value incorporating the minutes, etc., accurate measurement is always possible.

(Embodiment) A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a schematic diagram of the apparatus of the present invention.

Reference numeral 10 denotes Surin 1-glass, in which three slits A, B, and C are formed. Reference numeral 12 denotes a photosensor, which is arranged behind each slit A, B, and C. 14 is a floodlight lamp, which is arranged in front of the slits A, B, . Therefore, the light emitted from the floodlight lamp 14 passes through each slit A, 'B, and C and enters the corresponding photosensor 12.

The output signal from the photosensor 12 is input to a signal processing section including a CPU.

FIG. 2 is a schematic diagram of the signal processing section 16.

The output signal from the photosensor 12 is amplified by the operational amplifier 18, A/D converted by the A/D converter 22, inputted to the CPU 24, and written in the RAM of the CPU 24. In the CPU 24, in particular, the photo sensor 1
The maximum level value corresponding to the maximum amount of light received at step 2 is stored,
A predetermined value for this maximum level value, for example the maximum level value of 2, is output as the threshold level value. This threshold level value is D/A converted by the D/A converter 26 and applied to the input terminal of the comparator 20 as a base f voltage.

The output signal from the comparator 20 is input to the register, and the CPU 24 calculates the shutter speed based on this input signal.

The output signals from the three photosensors 12 are processed separately by configuring circuits each having the above configuration in parallel (note that the A/D converter 22
and the CPU 24 are shared).

FIG. 3 shows the signal levels of each part.

In the figure, T4, T5, and T6 are shutter speeds calculated along the paths passing through slits A1B and C, respectively.

Shutter speed is mainly evaluated by T5.

T4 is evaluated as an initial value, etc., and T6 is evaluated as a final value, etc. based on various criteria. Note that T7 and T8 are the running times of the first act and the second act between the slits Δ, B, and C, respectively. The speed of each of these curtains is also subject to various evaluations based on various criteria.

In this embodiment, the case where there are three slits is shown, but it is also possible to provide four or more slits to set various finer measurement points I.

The above-mentioned threshold level value is set each time a measurement is performed, that is, the threshold level value from the previous measurement is cleared, and the threshold level value is set based on the actual input signal from the object to be measured subsequently. Calculate each time (1/of the maximum level value
2, etc.), or only if the threshold level value calculated based on the signal from the following object deviates from the threshold level value measured previously, The threshold level value may be cleared and the subsequent threshold level value may be set as a new thread or threshold value. Alternatively, the threshold level value may be reset after measuring a predetermined number of samples, after a predetermined number of days have elapsed, or when a certain range has become buzzed. In the present invention, the timing of setting the threshold level is not particularly limited;
The point is that the threshold level value is not fixed;
The feature is that the threshold level value is newly set based on the maximum amount of light received.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and changes in several sets of details are included in the present invention as long as they do not depart from the spirit of the present invention. Of course, it is possible to

(Effects of the Invention) As described above, according to the present invention, the reference value of the comparator can be converted to a predetermined level based on the input signal during actual measurement. Even if there is a change in the amount of light from the light emitting lamp or the amount of light from the floodlight lamp, a new reference value is set that incorporates the change, etc., making accurate measurement possible at all times.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the apparatus of the present invention, FIG. 2 is a schematic diagram of its signal processing section, and FIG. 3 is a signal level diagram of each section. Figure 4 is a level diagram that does not show the amount of light received by the photosensor, Figure 5 is an explanatory diagram when determining the shutter speed using the differential method,
FIG. 6 is an explanatory diagram when determining the shutter speed using the level method. IO... Slit glass, 12... Photo sensor, A, B, C... Slit, 14... Flood lamp, 16... Signal processing section, 18... Amplifier,
22...A/D converter, 24...cpu, 26
...D/A converter. Figure 1

Claims (1)

[Claims] 1. A photo sensor is provided behind the slit of the slit plate, a floodlight is provided in front of the slit, and a focal plane shutter is run between the slit plate and the floodlight,
In a device that measures the accuracy of a shutter device by detecting light incident on a photosensor, an operational amplifier amplifies an output signal from the photosensor, and an amplified signal amplified by this operational amplifier is input, respectively. A comparator and an A/D converter, a signal A/D converted by the A/D converter is input, and an output signal is calculated in a predetermined range, such as 1/2 of the maximum level value of the input signal. and convert this output signal to D/
A focal plane that is input to the other input terminal of the comparator as a reference value via an A converter, and a CPU that receives an output signal from the comparator and calculates a shutter speed, etc. based on this input signal. Shutter accuracy measuring instrument.