JP2012002692A - Temperature detection apparatus, electronic flash apparatus, and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature detection apparatus that can accurately detect the temperature of a translucent member.SOLUTION: A temperature detection apparatus is provided with a translucent member 44 that transmits light from a light source 40; a transparent conductive film that is formed on the surface of the translucent member 44; and temperature detection means 42 that detects the temperature of the translucent member 44 based on the resistance value of the transparent conductive film.

Description

  The present invention relates to a temperature detection device, an electronic flash device, and a camera.

  A technique for preventing overheating of an electronic flash device used in a camera is known (see Patent Document 1). In an electronic flash device, a large amount of heat is generated at the same time as the arc tube emits light. Moreover, since the light energy emitted from the arc tube concentrates on the light transmitting member such as a Fresnel lens, the temperature of the light transmitting member rises. When a thermal sensor such as a thermistor or a thermocouple is directly disposed on the translucent member for temperature detection, a shadow of the sensor is generated. Therefore, a thermal sensor is disposed in a reflecting mirror that does not cause a shadow in the conventional technique.

JP 2003-255448 A

  However, when the thermal sensor is disposed at a position different from that of the translucent member, there is a problem that an accurate temperature of the translucent member is not known.

The temperature detection device according to the present invention includes a translucent member that transmits light from a light source, a transparent conductive film that has temperature dependency on resistivity, and is formed on the surface of the translucent member, and a resistance of the transparent conductive film. Temperature detecting means for detecting the temperature of the translucent member based on the value.
An electronic flash device according to the present invention has a predetermined temperature of the temperature detecting device according to any one of claims 1 to 4, a light emitting body that emits photographing auxiliary light, and a translucent member that transmits light from the light emitting body. And a notifying means for notifying that when the temperature detecting means detects that the temperature has been exceeded.
The camera by this invention is equipped with the electronic flash device as described in any one of Claims 5-7, It is characterized by the above-mentioned.

  According to the present invention, the temperature of the translucent member can be accurately detected.

1 is an external view of a camera system equipped with a flash device according to an embodiment of the present invention. It is a block diagram explaining the principal part structure of a camera system. It is a figure which illustrates the structure of a flash apparatus. It is a figure explaining the structure of a light emission part. It is the figure which looked at the translucent member from the to-be-photographed object side. It is a figure which illustrates the structure of a temperature detection circuit. It is a figure which illustrates the relationship between detection voltage and detection temperature. It is a figure explaining the example of wiring with respect to a transparent conductive film. It is a figure which illustrates the film-forming pattern of the transparent conductive film by the modification 2.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is an external view of a camera system equipped with a flash device according to an embodiment of the present invention. In FIG. 1, a replaceable photographing lens 20 is attached to the camera body 10. A release button 11 is provided on the upper left side when the camera body 10 is viewed from the subject side. A flash device 30 is attached to an accessory shoe (not shown) disposed at the upper center of the camera body 10.

  FIG. 2 is a block diagram for explaining a main configuration of the camera system of FIG. In FIG. 2, the flash device 30 performs a timing signal for instructing the start of light emission via a communication terminal 51 provided in the accessory shoe, a signal for instructing the amount of light emission, light emission preparation (during charging) and light emission preparation completion. A signal or the like indicated is transmitted to or received from the CPU 101.

  The CPU 101 is configured by an ASIC or the like. The CPU 101 inputs a signal output from each block described later, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block.

  The subject luminous flux that has entered the camera body 10 through the photographing lens 20 (FIG. 1) is guided to an imaging device (not shown) configured by a CCD image sensor, a CMOS image sensor, or the like via the shutter unit 105. The shutter unit 105 opens the shutter curtain at a predetermined timing in accordance with an instruction from the CPU 101 during shooting, and closes the shutter curtain when an exposure time corresponding to the shutter speed has elapsed.

  The operation member 107 includes a release switch that interlocks with the depression of the release button 11 (FIG. 1) and an operation switch group that performs various settings, and outputs an operation signal corresponding to the operation content to the CPU 101. For example, a setting operation signal is output to the CPU 101 in accordance with setting operations such as emission permission / prohibition of light emission to the flash device 30 and red-eye reduction light emission.

  The distance measuring device 102 detects a focus adjustment state by the photographing lens 20 and outputs a detection signal to the CPU 101. The focus adjustment information is acquired by, for example, a known phase difference detection method. The CPU 101 sends an instruction to the lens driving unit 104 to drive a focus lens (not shown) in the photographic lens 20 forward and backward in the optical axis direction according to the focus adjustment state, thereby adjusting the focal position of the photographic lens 20. The focus detection signal from the distance measuring device 102 is distance information corresponding to the distance to the main subject (shooting distance).

  The photometric device 103 detects the amount of subject light through the photographing lens 20 and outputs a detection signal to the CPU 101. The CPU 101 calculates subject luminance using the detection signal, and performs exposure calculation using the calculated luminance information. The CPU 101 can also perform exposure calculation by changing the ISO sensitivity.

  FIG. 3 is a diagram illustrating the configuration of the flash device 30. In FIG. 3, a flash device 30 includes a control circuit 31, a camera communication circuit 32, a booster circuit 33, a constant voltage circuit 34, a charge voltage detection circuit 35, a diode 36, a main capacitor 37, and a light emission control circuit. 38, a trigger circuit 39, a xenon arc tube 40, a voltage doubler circuit 41, a temperature detection circuit 42, an information display unit 43, and a translucent member 44, and a battery 60 is loaded.

  The control circuit 31 receives a signal output from each block in the flash device 30, performs a predetermined calculation, and outputs a control signal based on the calculation result to each block. The control circuit 31 communicates with the CPU 101 (FIG. 2) of the camera body 10 via the camera communication circuit 32. When a boost start signal is input via the communication terminal 51, the control circuit 31 instructs the boost circuit 33 to start boosting.

  The booster circuit 33 is configured by a DC-DC converter, and boosts the voltage of the battery 60 (for example, 330 V). The main capacitor 37 is charged via the diode 36 with the boosted voltage. When the charging voltage of the main capacitor 37 reaches the predetermined voltage Ve, the charging voltage detection circuit 35 notifies the control circuit 31 of the end of boosting. The control circuit 31 causes the information display unit 43 to light the pilot lamp and causes the camera communication circuit 32 to transmit a signal indicating that light emission preparation is complete to the CPU 101 (FIG. 2) of the camera body 10.

  The xenon arc tube 40 is controlled to discharge as follows. When a signal instructing light emission is transmitted from the CPU 101 of the camera body 10 via the communication terminal 51, the control circuit 31 sends an instruction to the light emission control circuit 38 and turns on the switching element 38a. When the switching element 38a is turned on, the voltage doubler circuit 41 generates a voltage more than twice the charging voltage of the main capacitor 37 between both electrodes of the xenon arc tube 40, thereby making the xenon arc tube 40 easier to emit light. . The trigger circuit 39 generates a trigger voltage when the switching element 38 a is turned on, and applies the trigger voltage to a trigger electrode (not shown) of the xenon arc tube 40. Xenon gas is excited in the xenon arc tube 40 by the applied trigger voltage, and an emission current of several tens of A to one hundred A or more flows in the xenon arc tube 40 in a short time, and the xenon arc tube 40 flashes. That is, the electrical energy stored in the main capacitor 37 is discharged through the xenon arc tube 40, thereby emitting photographing auxiliary light.

  The xenon arc tube 40 starts to emit light as soon as the switching element 38a is turned on, and its emission intensity increases to the maximum value. The emission intensity decreases as the stored energy in the main capacitor 37 decreases, and the emission ends when the stored energy in the main capacitor 37 becomes empty. In actual photographing, the power supply to the xenon arc tube 40 is stopped before all the stored energy is released, so that the light amount emitted from the xenon arc tube 40 is controlled to a predetermined light amount.

  The temperature detection circuit 42 detects a signal indicating the surface temperature of the translucent member 44 and sends the detection signal to the control circuit 31. The constant voltage circuit 34 generates a predetermined power supply voltage Vcc regardless of the remaining capacity of the battery 60 and supplies the voltage to the control circuit 31.

  FIG. 4 is a diagram illustrating the configuration of the light emitting unit. In FIG. 4, a reflecting mirror 46 is disposed so as to guide light forward of the xenon arc tube 40 (on the subject side and to the right in the drawing). The light reflected by the reflecting mirror 46 and the direct light from the xenon arc tube 40 are collected by the translucent member 44. The translucent member 44 is composed of, for example, a Fresnel lens, and distributes the light emitted from the xenon arc tube 40 to the subject side in a predetermined pattern.

  The xenon arc tube 40 is configured to be movable back and forth in the direction of the arrow in the figure, and the interval between the xenon arc tube 40 and the reflecting mirror 46 can be changed. Further, the interval between the reflecting mirror 46 and the translucent member 44 can also be changed. When a wide illumination angle of view is required, the interval between the xenon arc tube 40 and the reflecting mirror 46 or the reflecting mirror 46 and the translucent member 44 is narrowed, and when a narrow illumination angle of view is required, the xenon arc tube 40 and the reflecting mirror 46 or reflection. The interval between the mirror 46 and the translucent member 44 is increased.

  FIG. 5 is a view of the translucent member 44 as viewed from the subject side. On the surface of the translucent member 44, for example, a transparent conductive film 45 such as tin-doped indium oxide is formed. The transparent conductive film 45 is provided, for example, so as to cross the substantially central portion of the translucent member 44 to the left and right. The film formation position of the transparent conductive film 45 includes a region where the temperature is most likely to rise in the translucent member 44 (that is, a region where the energy density of light is high).

  FIG. 6 is a diagram illustrating a configuration of the temperature detection circuit 42. In FIG. 6, after the reference resistor 421 and the transparent conductive film 45 on the translucent member 44 are connected in series, the voltage Vcc is applied to these combined resistors. The temperature detection circuit 42 detects the voltage V based on the resistance value R45 of the transparent conductive film 45.

The detection voltage V is calculated by the following equation (1).
V = Vcc × R45 / (R421 + R45) (1)
However, Vcc is a voltage supplied from the constant voltage circuit 34. R421 is the resistance value of the reference resistor 421.

  FIG. 7 is a diagram illustrating the relationship between the detection voltage V and the detection temperature (surface temperature of the translucent member 44). The resistivity of the tin-doped indium oxide constituting the transparent conductive film 45 has temperature dependence. For this reason, the resistance value R45 of the transparent conductive film 45 increases as the temperature of the translucent member 44 increases, and the detected temperature V increases as the temperature increases. The detection temperature V may be read, for example, immediately after the end of one light emission by the xenon arc tube 40 (to prevent erroneous recognition due to electromagnetic wave noise during light emission). For example, the control circuit 31 stores an LUT (lookup table) configured to read the detected temperature using the detected voltage V as an argument in an internal nonvolatile memory in advance. The control circuit 31 uses the detection signal from the temperature detection circuit 42 to acquire the surface temperature of the translucent member 44 from the LUT. Note that a function having the detected voltage V as a variable may be stored instead of storing the lookup table. In this case, the surface temperature of the translucent member 44 is calculated by substituting the detection voltage V into a variable.

  FIG. 8 is a diagram for explaining a wiring example of the wiring members 49a and 49b with respect to the transparent conductive film 45. FIG. Conductive rubbers 47 a and 47 b are bonded to the transparent conductive film 45 at both ends (corresponding to the left and right ends in FIG. 5) of the translucent member 44. Then, the wiring boards 48 a and 48 b are further bonded so that the conductive rubber 47 a and 47 b are sandwiched between the translucent member 44. Wiring materials 49a and 49b are soldered to the wiring boards 48a and 48b, respectively. One of the wiring members 49 a and 49 b is connected to GND, and the other is connected to the reference resistor 42. This is an example for connecting the resistance value of the transparent conductive film 45 to the temperature detection circuit, and the present invention is not limited to this.

  The surface temperature of the translucent member 44 increases as the discharge energy per unit time by the xenon arc tube 40 increases. Specifically, the temperature tends to rise when continuous flash photography is performed to cause the flash device 30 to emit light. When the detected temperature reaches a temperature lower by a predetermined value than the material softening temperature lower than the melting point of the material constituting the translucent member 44, the control device 31 sends an instruction to the camera communication circuit 32 and transmits the instruction to the CPU 101 on the camera body 10 side. The temperature rise of the optical member 44 is transmitted.

  Further, the control circuit 31 notifies the photographer of the temperature rise of the translucent member 44 by displaying on the information display unit 43 the temperature rise of the translucent member 44. For example, the photographer can take measures such as shooting without causing the flash device 30 to emit light.

  On the other hand, the camera body 10 to which the temperature rise of the translucent member 44 has been transmitted, for example, increases the ISO sensitivity and lowers the amount of light that is newly instructed to the flash device 30, thereby suppressing further temperature rise. 30 is controlled.

  Further, the camera body 10 to which the temperature rise of the translucent member 44 has been transmitted changes the shooting angle of view narrower, and narrows the illumination angle of view newly instructed to the flash device 30. That is, the flash device 30 is controlled so as to suppress further temperature rise by widening the gap between the xenon arc tube 40 and the reflecting mirror 46 or the translucent member 44.

According to the embodiment described above, the following operational effects can be obtained.
(1) The temperature detection unit of the flash device 30 includes a translucent member 44 that transmits light from the xenon arc tube 40 and a temperature dependency on resistivity, and is formed on the surface of the translucent member 44. A conductive film 45 and a temperature detection circuit 42 that detects the temperature of the translucent member 44 based on the resistance value R45 of the transparent conductive film 45 are provided. Thereby, the temperature of the translucent member 44 can be detected directly and accurately without causing a shadow by the transparent conductive film 45. Since accurate detection is possible, it is not necessary to secure a large margin as compared with the case of estimating the temperature of the translucent member 44 from the detected temperature of other members other than the translucent member 44, so that the temperature rise is within the allowable range. The flash can be emitted until

(2) Since the transparent conductive film 45 is composed of tin-doped indium oxide, it is possible to appropriately detect the temperature of the translucent member 44 while suppressing attenuation of light from the xenon arc tube 40.

(3) Since the transparent conductive film 45 is formed on one surface of the translucent member 44, the transparent conductive film 45 can be configured more easily than when formed on both surfaces.

(4) In the flash device 30, the temperature of the above-described temperature detection unit, the light emitter xenon arc tube 40 that emits photographing auxiliary light, and the translucent member 44 that transmits the light from the xenon arc tube 40 exceed a predetermined temperature. An information display unit 43 is provided for informing the user when the temperature is detected by the temperature detection unit. As a result, the photographer can deal with avoiding further temperature rise such as shooting without causing the flash device 30 to emit light.

(5) The predetermined temperature is a temperature for changing the ISO sensitivity of the camera body 10 to be high and reducing the amount of the photographing auxiliary light in accordance with the change in the ISO sensitivity, so that the photographer does not notice the temperature rise. However, further temperature rise can be prevented. In addition, insufficient exposure due to a reduction in the amount of photographing auxiliary light can be compensated by increasing ISO sensitivity.

(6) The predetermined temperature is a temperature for narrowing the shooting field angle of the camera body 10 and changing the illumination field angle of the auxiliary shooting light according to the change of the shooting field angle. Even if the temperature rise is not noticed, further temperature rise can be prevented. In addition, a mismatch between the illumination field angle and the shooting field angle can be prevented.

(Modification 1)
The shape of the transparent conductive film 45 formed on the surface of the translucent member 44 is not limited to that illustrated in FIG. 5, and may be formed so as to cover the surface of the translucent member 44. Note that when wiring members 49a and 49b are wired to the left and right ends of the translucent member 44 illustrated in FIG. 5, the resistance value R45 of the transparent conductive film 45 is mainly a straight line connecting the wiring member mounting portions at both the left and right ends. Therefore, the linear portion is configured to coincide with the region where the temperature rises most easily.

(Modification 2)
Further, the shape of the transparent conductive film 45 formed on the surface of the translucent member 44 may be spiral as illustrated in FIG. In the case of FIG. 9, all of the spiral pattern of the transparent conductive film 45 contributes to the resistance value R45. The wiring positions of the wiring members 49 a and 49 b in the case of FIG. 9 are both the left end of the translucent member 44.

(Modification 3)
In the case where the two translucent members 44 are stacked, a transparent conductive film may be sandwiched between the first translucent member and the second translucent member.

(Modification 4)
Although the example using the xenon arc tube 40 as the light emitter of the flash device 30 has been described, a discharge arc tube other than the xenon arc tube 40 may be used as the light emitter. Further, an LED light source may be used instead of the discharge arc tube.

(Modification 5)
The translucent member 44 is not limited to the Fresnel lens, and may be applied to other optical members such as a filter.

(Modification 6)
The present invention may be applied not only when the flash device 30 is directly attached to the camera body 10 but also when light emission control is performed between the camera body 10 and the flash device 30 via wireless communication. Even when the flash device 30 is not disposed in the vicinity of the photographer and the photographer cannot directly check the information display unit 43 provided in the flash device 30, the temperature increase of the translucent member 44 is photographed by wireless communication. Can tell.

(Modification 7)
The present invention may be applied not only to the flash device 30 but also to a camera incorporating the flash device. The present invention may also be applied to a projector device that generates heat in the light source unit.

(Modification 8)
Although tin-doped indium oxide (ITO) has been described as a structural example of the transparent conductive film 45, antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), and aluminum are other structural examples having transparency and conductivity. Doped zinc oxide (AZO) or the like can be used. Further, a polymer film containing fine gold fibers or magnesium may be used.

  The above description is merely an example, and is not limited to the configuration of the above embodiment.

DESCRIPTION OF SYMBOLS 10 ... Camera body 30 ... Flash apparatus 31 ... Control circuit 32 ... Camera communication circuit 33 ... Booster circuit 37 ... Main capacitor 38 ... Light emission control circuit 40 ... Xenon arc tube 42 ... Temperature detection circuit 43 ... Information display part 44 ... Translucent member 45 ... Transparent conductive film 46 ... Reflector

Claims (8)

A translucent member that transmits light from the light source;
A transparent conductive film having a temperature dependency on resistivity and formed on the surface of the translucent member;
Temperature detecting means for detecting the temperature of the translucent member based on the resistance value of the transparent conductive film;
A temperature detecting device comprising: The temperature detection device according to claim 1,
The temperature detecting device, wherein the transparent conductive film is made of tin-doped indium oxide. The temperature detection device according to claim 1 or 2,
The temperature detecting device, wherein the transparent conductive film is formed on one surface of the translucent member. The temperature detection device according to claim 1 or 2,
The temperature detecting device, wherein the transparent conductive film is formed between a first light transmissive member and a second light transmissive member constituting the light transmissive member. The temperature detection device according to any one of claims 1 to 4,
An illuminant that emits shooting assistance light;
Informing means for notifying the case where the temperature detecting means detects that the temperature of the translucent member that has transmitted light from the light emitter exceeds a predetermined temperature;
An electronic flash device comprising: The electronic flash device according to claim 5,
The electronic flash device according to claim 1, wherein the predetermined temperature is a temperature for changing the ISO sensitivity of the camera to be high and reducing the amount of the photographing auxiliary light according to the change of the ISO sensitivity. The electronic flash device according to claim 5,
The electronic flash device characterized in that the predetermined temperature is a temperature for changing a shooting field angle of the camera narrowly and changing an illumination field angle of the photographing auxiliary light in accordance with the change of the shooting field angle. .   A camera comprising the electronic flash device according to claim 5.

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