JP3400585B2 - Camera detection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera adjusting device.

[0002]

2. Description of the Related Art A conventional camera detection device is shown in FIG.
A control circuit (hereinafter referred to as CPU) 41 controls the entire system as a whole, and includes a read-only memory (hereinafter referred to as ROM) 41a and a random access memory (hereinafter referred to as R).
41b inside).

The CPU 41 includes a photometric circuit 42 for detecting the brightness of the subject and its surroundings, a distance measuring circuit 42 for detecting the distance to the subject, a temperature detecting circuit 46 for detecting the ambient temperature, and a film for detecting the sensitivity of the film. Several detection means such as the sensitivity reading terminal 45 are directly or indirectly connected.

Of these, the photometric circuit 42 converts the luminance Ev of the subject and its surroundings into an electric signal by the function of a photoconductive cell (hereinafter referred to as CDS) 42a and outputs the electric signal to an amplifier 42d, which is logarithmically converted. And outputs it to the A / D converter 47 via the switch 47a. A /
The D converter 47 converts this electric signal into a digital value and outputs it to the CPU 41, and the CPU 41 calculates the brightness based on the output of the A / D converter 47.

The temperature detection circuit 46 is a thermistor 46.
The function of a converts the ambient temperature into a signal and outputs it to the logarithmic conversion amplifier 46d. The logarithmic conversion amplifier 46d logarithmically converts this signal and outputs it to the A / D converter 47. A / D
The converter 47 converts this electric signal into a digital value and outputs it to the CPU 41, and the CPU 41 outputs the A / D converter 4
The brightness is calculated based on the output of 7.

[0006]

However, in the above-mentioned configuration, the amplifier 42d and the logarithmic conversion amplifier 46d having substantially the same circuit configuration must be provided in the system. It is disadvantageous and leads to higher costs.

[0007]

In order to solve the above-mentioned problems, in a camera adjusting device of the present invention, a light-sensitive element whose electric resistance changes according to ambient light and a first resistance are used as a power source.
A first series circuit that is connected between grounds and outputs the voltage at the contact point of the light-sensitive element and the first resistor, a temperature-sensitive element whose electric resistance changes according to the ambient temperature, and a second resistor are power supplies. A second series circuit connected between ground and outputting the voltage at the contact point of the temperature sensitive element and the second resistor; and the first series circuit.
Of the serial circuit or the second series circuit, a selecting means, an analog / digital converting circuit for analog / digital converting the output selected by the selecting means, and an analog / digital converting circuit. It has a storage means having a logarithmic conversion table for logarithmically converting the output, and an arithmetic means for selectively calculating the brightness of ambient light and the ambient temperature from the outputs of the analog / digital conversion circuit and the storage means. There is.

According to the second aspect of the invention, the photosensitive element whose one end changes its electric resistance in accordance with the ambient light connected to the power source, and the one end whose electric resistance changes in accordance with the ambient temperature connected to the power source. Of the temperature-sensitive element, selection means for selecting either the light-sensitive element or the other end of the temperature-sensitive element, a logarithmic compression circuit for logarithmically compressing the output selected by the selection means, and a logarithmic compression circuit. An amplifier circuit for amplifying the output, an analog / digital converter circuit for analog / digital converting the output of the amplifier circuit, and an operation for selectively calculating the brightness of ambient light and the ambient temperature from the output of the analog / digital converter circuit. And means.

[0009]

The logarithmic conversion circuit included in the brightness detection circuit and the temperature detection circuit is omitted, and the value obtained by directly A / D converting the output of the detection element is compared with the conversion table in the ROM 1a.
Calculate brightness or temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a camera adjusting device of the present invention.
Shown in. The same parts as those in the conventional example are designated by the same reference numerals.
The CPU 1 centrally controls the entire system and internally has a ROM 1a for holding programs and data, and a RAM 1b used for calculation and temporary storage. A luminance conversion table TL shown in FIG. 2A and a temperature conversion table TT shown in FIG. 2B are prepared in advance in the ROM 1a. The brightness conversion table TL and the temperature conversion table TT will be described later. The photometric circuit 2 converts the intensity of light received by the photometric element 2a into a signal and outputs the signal to the CPU 1. The distance measuring circuit 3 is a so-called active type distance measuring device. Since the light emitted from the pulse-driven light projecting element 3a is reflected on the subject and enters the light receiving element 3b, the output signal of the light receiving element 3b is amplified. The signal is converted and output to the CPU 1. The CPU 1 calculates the distance to the subject based on this signal. The motor 4 drives the lens barrel 4a to the in-focus position. The film sensitivity reading terminal 5 reads a known DX pattern which is printed in advance on the film cartridge, and the CP
U1 determines the sensitivity of the film based on this. The brightness detection circuit 6 detects the ambient temperature using the thermistor 6a included in the brightness detection circuit 6. The thermistor 6a is an element whose resistance changes according to a change in temperature.

The photometry circuit 2 and the brightness detection circuit 6 will be described below. First, the photometric circuit 2 comprises a photometric element 2a whose one end is connected to a power source and a voltage dividing resistor 2b whose one end is grounded. The brightness of the subject is output to the contact point of the photometric element 2a and the voltage dividing resistor 2b. It The voltage dividing resistor 2b is the photometric element 2
In addition to dividing the voltage of a to obtain an appropriate output voltage, it also has a function of preventing the photometric element 2a from being destroyed or deteriorated by an unnecessarily large current flowing at the time of high brightness. The output voltage is directly taken into the A / D converter 7 through the switch 7a, and the A / D converter 7 converts this voltage into a digital value and outputs it to the CPU 1. The CPU 1 refers to the brightness conversion table shown in FIG. 2A which is built in the ROM 1a in advance, and determines the brightness of the subject or its surroundings.

The brightness detecting circuit 6 has the same structure as the photometric circuit 2. The brightness detection circuit 6 includes a thermistor 6a having one end connected to a power source, and a voltage dividing resistor 6 having one end grounded.
The brightness of the subject is output to the contact point between the photometric element 2a and the voltage dividing resistor 6b. The output voltage is switch 7
A is directly taken into the A / D converter 7 through
The D converter 7 converts this voltage into a digital value and CP
Output to U1. The CPU 1 refers to the temperature conversion table shown in FIG. 2B which is built in the ROM 1a in advance and determines the ambient temperature.

The meaning of determining the temperature by the temperature determining circuit is mainly for compensating the temperature characteristics of electric parts and mechanical parts. For example, since the light projecting element 3a is a diode,
Even if the same voltage is applied, the emission brightness varies depending on the temperature. Generally, when the temperature is high, the brightness is lowered, so that the distance measurement accuracy is deteriorated when the subject is at a long distance. In such a case, the distance measuring accuracy can be prevented from deteriorating by taking measures such as increasing the voltage applied to the light projecting element 3a according to the temperature.

Next, the operation of this embodiment will be described. When the photographer presses the release switch 8, the CPU 1 first uses the brightness detection circuit 6 to detect the ambient temperature. Then CPU
Reference numeral 1 causes the photometry circuit 2 to perform a photometry operation, and then the distance measurement circuit 3 to perform a distance measurement operation to obtain luminance information and distance information from each.
When the optimum exposure condition is calculated from the information and the film sensitivity, the lens barrel 4a is moved to the in-focus position, and the shutter 9 is driven through the terminal 9a to perform the exposure.

In the present embodiment, the photometric element 2a and the thermistor 6a are connected to the power source, and the voltage dividing resistor is connected to the ground. On the contrary, the photometric element 2a and the thermistor 6a are connected to the power source by the voltage dividing resistor. You may.

Further, if it is constructed as shown in FIG. 3, the voltage dividing resistor 2b and the thermistor 6a can be shared.

Next, a second embodiment of the present invention will be described with reference to FIG. The block diagram of the second embodiment is as shown in FIG. 4, and the same parts as those in the first embodiment are designated by the same reference numerals. One end of each of the photometric element 2a and the thermistor 6a is connected to a power source, and the other end can be selected by the switch 10a. The voltage generated by the element selected by the switch 10a and the grounded diode 10b is output to the amplifier 10c. The resistance values of the photometric element 2a and the thermistor 6a change in a wide range depending on the brightness and the temperature, respectively, and thus the current amount also largely changes, but this is converted into a logarithmic voltage change by utilizing the forward voltage characteristic of the diode. Converting.

The amplifier 10c amplifies this signal and outputs it to the A / D converter 7. The A / D converter 7 converts this into a digital value and outputs it to the CPU 1. CPU1 is R
The brightness of the subject or its surroundings is determined by referring to the brightness conversion table shown in FIG. 2A which is built in the OM 1a in advance.

[0019]

As described above, the output of the detection circuit is directly read by the A / D converter, and its output value is RO.
By referring to the conversion table in M, the logarithmic conversion circuit required for each circuit can be reduced. Therefore, the space is reduced, which is advantageous in terms of cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a brightness and temperature conversion table of a ROM 1a.

FIG. 3 is a modification of the block diagram of the first embodiment of the present invention.

FIG. 4 is a block diagram of a second embodiment of the present invention.

FIG. 5 is a block diagram of a conventional camera detection device.

[Explanation of symbols]

2a Photometric element 2b Voltage dividing resistance (first resistance) 6a thermistor 6b Voltage dividing resistance (second resistance) 7a switch 7 A / D converter 1a ROM (storage means) 1 CPU (calculation means)

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryuichi Oka 934-13 Shikato, Yotsukaido-shi, Chiba Seikosha Co., Ltd. Chiba Works (56) References JP-A-1-156630 (JP, A) −95931 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01J 1/42-1/46 G03B 7/08-7/099 H01L 31/10 H04N 5/30-5 / 335

Claims (2)

(57) [Claims] 1. A light-sensitive element whose electric resistance changes according to ambient light and a first resistor are connected between a power source and a ground to output a voltage at a contact point between the light-sensitive element and the first resistor. 1
A series circuit, a temperature sensitive element whose electric resistance changes according to the ambient temperature, and a second resistor are connected between a power source and ground, and the voltage at the contact point of the temperature sensitive element and the second resistor is output. Two series circuits, and selection means for selecting an output of either the first series circuit or the second series circuit,
An analog / digital conversion circuit for analog / digital converting the output selected by the selection means, a storage means having a logarithmic conversion table for logarithmically converting the output of the analog / digital conversion circuit, and the analog / digital conversion circuit.
Ambient light from the output of the digital conversion circuit and the storage means
And a calculation means for selectively calculating the brightness and ambient temperature of the camera. 2. A photosensitive element, one end of which has an electric resistance that changes according to ambient light connected to a power supply, and one end of which has a temperature sensitive element, whose electric resistance changes according to an ambient temperature. Selecting means for selecting either the light sensitive element or the other end of the temperature sensitive element; a logarithmic compression circuit for logarithmically compressing the output selected by the selecting means; and an amplifier circuit for amplifying the output of the logarithmic compression circuit. An analog / digital conversion circuit for analog / digital converting the output of the amplifier circuit, and an arithmetic means for selectively calculating the brightness of ambient light and the ambient temperature from the output of the analog / digital conversion circuit. And a detection device for a camera.