JP2008309732A - Light detection device and optical equipment using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light detection device capable of increasing the area of a photodiode without allowing deterioration of response speed in power-on, and optical equipment using the same. <P>SOLUTION: The device includes a light source detection sensor 8 having a visible light detecting photodiode 9-2 and an infrared light photodiode 9-1 sensitive to visible light and infrared right, which include an IR cut filter 10 and a visible light cut filter 11 disposed on the respective front surfaces; and a LED 12 emitting infrared ray in a position inclined to the light source detection sensor, and is configured so that the infrared ray from the LED is directly incident on the visible light detecting photodiode and the infrared ray detecting photodiode without passing through the visible light cut filter and the IR cut filter. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light detection device that shortens the time required for the output voltage to stabilize after power is turned on, and an optical apparatus using the same.

  As a light detection circuit used for a photometric sensor such as a camera, a circuit disclosed in, for example, Japanese Patent Laid-Open No. 5-180695 has been known. The configuration of the photodetection circuit disclosed in the above publication will be described with reference to FIG. As shown in FIG. 7, the photodetector circuit disclosed in the above publication has a photodiode 9 as a light receiving element connected between the input terminals of the operational amplifier 14 and is used for logarithmic compression between the inverting input terminal and the output terminal of the operational amplifier 14. The diode 13 is connected, and the non-inverting input terminal of the operational amplifier 14 is connected to the reference voltage source 15. The photocurrent generated by receiving light at the photodiode 9 is logarithmically compressed by the diode 13 and converted into a voltage, and then output from the output terminal 16. Note that a parasitic capacitance (junction capacitance) is added in parallel to the diode 13 and the photodiode 9.

In the conventional photodetection circuit having the above-described configuration shown in FIG. 7, the state from when the power is turned on until the output voltage is stabilized is shown in FIG. In the photodetection circuit having the above configuration, the time t ₀ required from when the power is turned on until the output voltage is stabilized is expressed by the following equation (1).
t ₀ = {C ₁ · (V ₁ −V ₀ ) / A ₀ + C ₂ · (V ₁ −V ₀ )} / i
・ ・ ・ ・ ・ ・ ・ (1)

Here, A ₀ is the open loop gain of the operational amplifier, C ₁ is the junction capacitance of the photodiode 9, V ₁ is the output voltage when the power is turned on, V ₀ is the output voltage after stabilization, and C ₂ is the parasitic capacitance of the diode 13. , I is the current value of the photocurrent generated by the photodiode 9. As shown in FIG. 8, after the power is turned on, the output voltage is V ₁ for the time t ₀₂ and then stabilizes toward the output voltage V ₀ for the time t ₀₁ .

In the above publication, a configuration is shown in which n diodes 13 are connected in series to make the parasitic capacitance C ₂ have a capacitance value of 1 / n compared to the case of one diode. When the influence of the parasitic capacitance is reduced, the response time t ₀ when the power is turned on is shortened.
Japanese Patent Laid-Open No. 5-180695

However, the light detection circuit disclosed in the above publication has the following problems. That is, in the conventional example of the above publication discloses, not been consideration for the junction capacitance C ₁ response speed of degradation of the power-on due to the photodiode. In order to operate the light detection circuit with lower luminance, it is necessary to increase the area of the photodiode in order to increase the photocurrent. When the photodiode is increased, the junction capacitance is increased. In this case, (1) for formula junction capacitance C ₁ of the photodiode becomes large, t ₀₁ is output without waiting for a long time after increased and the power is turned on is not stable.

  The present invention has been made paying attention to this point, and is a photodetection device capable of solving the problem that the area of the photodiode is increased, the junction capacitance is increased, and the response speed is deteriorated when the power is turned on. An object of the present invention is to provide an optical instrument using the above.

  In order to solve the above-described problem, an invention according to claim 1 is directed to an operational amplifier, an element having a logarithmic compression characteristic connected between an input terminal and an output terminal of the operational amplifier, and an input terminal of the operational amplifier. An optical signal reading unit having a connected light receiving element, and a light supply unit that supplies the light receiving element with an amount of light that sets the signal level of the output terminal to a predetermined level within a set time when the power is turned on. Thus, the light detection device is configured. The embodiment of the invention according to claim 1 corresponds to the first embodiment.

  According to a second aspect of the present invention, in the optical detection device according to the first aspect, the optical signal readout unit includes two optical signal readout units, and one of the optical signal readout units is incident on the front surface of the light receiving element. A filter that removes infrared light components of light is disposed, and the other optical signal readout unit is disposed with a filter that removes visible light components of incident light on the front surface of the light receiving element, and the light supply means includes A part or all of the supplied light is arranged at a position where it directly enters each of the light receiving elements of the two optical signal readout units. The embodiment of the invention according to claim 2 corresponds to the first embodiment.

  According to a third aspect of the present invention, in the light detection device according to the second aspect, the light receiving element of each of the one and the other optical signal readout units is a photoelectric conversion element having sensitivity to visible light or infrared light, The light supply means is an infrared light emitting element or a visible light emitting element. The embodiment of the invention according to claim 3 corresponds to the first embodiment.

  The invention according to claim 4 has a light emitting element for displaying an operation state, and the light detection device according to any one of claims 1 to 3, wherein the light emitting element supplies light to the light detection device. It is used as a means to constitute an optical apparatus. Embodiments 2 and 3 correspond to the embodiment of the invention according to claim 4.

  According to the first aspect of the present invention, the response time when the power is turned on can be shortened by supplying the light receiving element of the light detection device with a light amount necessary for turning on the power. According to the second aspect of the present invention, the light supply means is arranged at a position where the supply light directly enters each of the light receiving elements of the one optical signal readout unit and the other optical signal readout unit, so that It is possible to operate the light detection device by supplying light without leakage and shortening the response time when the power is turned on. According to the invention of claim 3, by using the infrared light emitting element or the visible light emitting element as the light supply means, the necessary light is supplied to each of the one optical signal readout unit and the other optical signal readout unit. Thus, the response time when the power is turned on can be shortened, and the photodetection device can be operated. According to the invention of claim 4, it becomes possible to use the light emitting element for displaying the operation state as a light supply means for shortening the response time when the light detection device is turned on. The number of component parts of the device can be reduced.

  Next, the best mode for carrying out the present invention will be described.

Example 1
First, a first embodiment of the light detection device according to the present invention will be described. The photodetecting device according to the first embodiment will be described with reference to FIGS. Embodiment 1 is a configuration example in which a light detection device according to the present invention is mounted on a camera as a light source detection sensor for determining a light source type. FIG. 1 is an external view of a camera equipped with a light source detection sensor. In FIG. 1, a camera body 5 has a power switch button 0 and a shutter button 1 for controlling power ON / OFF at the upper left end of the camera body 5, and a light source detection sensor for discriminating a light source type at the time of photographing. The provided light source detection unit 2 is disposed on the upper left side of the interchangeable lens 4.

  Next, a method for supplying light to the light source detection sensor will be described with reference to FIG. A light source detection sensor 8 is disposed behind the diffusion window 7 for the light source detection sensor provided on the exterior 6 of the camera. The LED 12 that emits infrared light supplies infrared light from a position inclined with respect to the light source detection sensor 8.

  In the light source detection sensor 8, a visible light detection photodiode 9-2 having sensitivity to visible light or infrared light is arranged in a visible light detection optical signal reading unit, and infrared light of incident light is arranged on the light incident side. An IR cut filter 10 for removing components is disposed. In addition, an infrared light detection photodiode 9-1 having sensitivity to visible light or infrared light is arranged in the infrared light detection optical signal readout unit, and the visible light component of the incident light is placed on the light incident side. A visible light cut filter 11 to be removed is arranged and configured. The light source type is determined based on the ratio of the output of the infrared light detection photodiode 9-1 of the light source detection sensor 8 to the output of the visible light detection photodiode 9-2. Based on the determination result of the light source type, highly accurate focus deviation correction and white balance correction are performed.

  Next, the optical signal reading unit of the light source detection sensor 8 which is the light detection apparatus according to the first embodiment will be described with reference to FIG. As shown in FIG. 3, infrared light detection and visible light detection photodiodes 9-1 and 9-2 are connected between input terminals of operational amplifiers 14-1 and 14-2, respectively, and diodes 13-1, 13-2 is connected between the inverting input terminals of the operational amplifiers 14-1 and 14-2 and the output terminals 16-1 and 16-2, respectively, and the non-inverting input terminals of the operational amplifiers 14-1 and 14-2 are connected to the reference voltage. An optical signal readout unit is configured by connecting to the source 15.

Further, the LED 12 for emitting infrared light shown in FIG. 2 is turned on when the power switch button 0 is turned on, and irradiates the light source detection sensor 8 with infrared light from an oblique direction. In addition, a necessary amount of light that does not pass through the visible light cut filter 11 is directly supplied to both the infrared light detection photodiode 9-1 and the visible light detection photodiode 9-2. Thus, when the power switch button 0 is turned on and light is supplied to each photodiode, the time t ₀ required for the output to stabilize after the power is turned on as described in the equation (1) is determined from the LED 12. If the supplied light photocurrent generated in each photodiode and i _LED, it is expressed by the following equation (2).
t ₀ = {C ₁ · (V ₁ −V ₀ ) / A ₀ + C ₂ . (V ₁ −V ₀ )} / (i + i _LED )
<{C ₁ · (V ₁ −V ₀ ) / A ₀ + C ₂ . (V ₁ −V ₀ )} / i
(2)

  As can be seen from the equation (2), when the power switch button 0 is turned on, the infrared light is supplied from the LED 12 to the photodiode, thereby shortening the time required for normal operation after turning on the power.

(Example 2)
Next, Example 2 will be described with reference to FIGS. As shown in FIG. 4A, in the camera using the light detection device according to the second embodiment, the power switch button 0 is provided on the upper part of the camera body 5, and the self-timer operation display unit is provided below the light source detection unit 2. 3 is arranged. The configuration other than the self-timer operation display unit 3 in the camera shown in FIG. 4A is the same as the configuration of the camera using the photodetecting device according to the first embodiment shown in FIG. In the second embodiment, a light-emitting element applied to the self-timer operation display unit 3 is used as a light supply unit of the light detection device. As shown in FIG. 4B, in the self-timer operation display unit 3, a light emitting element 19 for displaying the operation is arranged inside the exterior 6 of the camera.

  As the light emitting element 19, an element having sensitivity of visible light to near infrared light is used in order to display the operation state of the self-timer to the photographer. The light emitted through the projection window 17 displays the operating state when the camera performs self-timer shooting or remote control operation. Then, the leakage light of the light emitting element 19 is reflected by the reflecting member 18 so that the light is supplied to the light source detection sensor 8 from an oblique direction. By supplying light to the light source detection sensor 8 from an oblique direction, light that does not pass through the visible light cut filter 11 is directly supplied to the infrared light detection photodiode 9-1. On the other hand, in the visible light detecting photodiode 9-2, the light of the light emitting element 19 has sensitivity to visible light, and not only the light directly incident from an oblique direction without passing through the IR cut filter 10, Photocurrent is also generated by the light transmitted through the IR cut filter 10.

  As described above, also in Example 2, the light emitting element 19 is turned on when the power switch button 0 is turned on, and the photocurrent is detected in each of the visible light detection photodiode and the infrared light detection photodiode of the light source detection sensor. By generating the same as in the first embodiment, it is possible to shorten the response time when the light detection device is turned on as shown in the equation (2).

(Example 3)
Next, Example 3 will be described with reference to FIGS. In the third embodiment, a light emitting element for a card access state display unit is used as a light supply unit of the light detection device. FIG. 5 is a diagram of a camera using the light detection device according to the third embodiment as viewed from the back. In this camera, a power switch button 0 for controlling ON / OFF of the power supply is provided, and a card access state display unit 21 for displaying the access state of the camera to the memory card and the normal operation when the power is turned on is provided on the camera. A liquid crystal monitor 20 for displaying a photographed image is arranged at the center on the back of the camera, which is arranged on the upper right part of the back of the body 5.

  Next, a method of supplying light to the light source detection sensor 8 by the light emitting element used for the card access state display unit 21 will be described with reference to FIG. In the third embodiment, the card access state display unit 21 is provided with a light emitting element 23 for a card access state display unit having sensitivity of visible light to infrared light inside a light projection window 25 for the card access state display unit. The leakage light of the light-emitting element 23 for the card access state display unit is supplied from the oblique direction to the light source detection sensor 8 through the reflecting members 22 and 24.

  In the camera equipped with the light detection device configured as described above, when the power switch button 0 is turned on, the light from the light emitting element 23 is supplied to the light source detection sensor 8 from an oblique direction, so that visible light can be obtained. Light that does not pass through the cut filter 11 is directly supplied to the infrared light detection photodiode 9-1 and light that does not pass through the IR cut filter 10 is directly supplied to the visible light detection photodiode 9-2. As shown in the equation (2), the response time when the light detection device is turned on can be shortened.

  It should be noted that the configuration of each of the above embodiments of the present invention can be variously modified and changed, and is not limited to the above description. Moreover, the same code | symbol is attached | subjected and shown to the component which is common in each Example.

It is an external view which shows the structure of the camera which mounts Example 1 of the photon detection apparatus which concerns on this invention as a light source detection sensor. FIG. 2 is a diagram showing a mode of supplying light to a light source detection sensor in the camera shown in FIG. 1. FIG. 3 is a circuit configuration diagram illustrating a configuration of an optical signal reading unit in the photodetecting device according to the first embodiment. It is a figure which shows the external appearance which shows the structure of the camera which mounts Example 2 of the optical detection apparatus based on this invention as a light source detection sensor, and the supply aspect of the light to a light source detection sensor. It is a rear view which shows the structure of the camera which mounts Example 3 of the optical detection apparatus which concerns on this invention as a light source detection sensor. FIG. 6 is a diagram illustrating how light is supplied to a light source detection sensor in the camera illustrated in FIG. 5. It is a circuit block diagram which shows the structural example of the conventional photon detection circuit. FIG. 8 is a diagram illustrating a mode from power-on until the output voltage is stabilized in the light detection circuit illustrated in FIG. 7.

Explanation of symbols

0 Power switch button 1 Shutter button 2 Light source detection unit 3 Self-timer operation display unit 4 Interchangeable lens 5 Camera body 6 Camera exterior 7 Light source detection sensor diffusion window 8 Light source detection sensor 9-1 Infrared light detection photodiode 9-2 Visible light detection photodiode
10 IR cut filter
11 Visible light cut filter
12 LED
13-1, 13-2 Diode
14-1, 14-2 Operational amplifier
15 Reference voltage source
16-1, 16-2 output terminals
17 Floodlight window
18 Reflective member
19 Light emitting element
20 LCD monitor
21 Card access status display
22, 24 Reflective member
23 Light emitting element
25 Floodlight window

Claims (4)

An optical signal readout unit including an operational amplifier, an element having a logarithmic compression characteristic connected between an input terminal and an output terminal of the operational amplifier, and a light receiving element connected to the input terminal of the operational amplifier;
And a light supply unit configured to supply a light amount to the light receiving element so that a signal level of the output terminal is a predetermined level within a set time when the power is turned on.   The optical signal readout unit includes two optical signal readout units, and one of the optical signal readout units is provided with a filter for removing an infrared light component of incident light on the front surface of the light receiving element, and the other of the light components. The signal readout unit is provided with a filter that removes visible light components of incident light on the front surface of the light receiving element, and the light supply unit is configured such that a part or all of the supplied light is supplied to each of the two optical signal readout units. The photodetecting device according to claim 1, wherein the photodetecting device is disposed at a position directly incident on the light receiving element. The light receiving element of each of the one and other optical signal readout units is a photoelectric conversion element having sensitivity to visible light to infrared light,
The light detection device according to claim 2, wherein the light supply unit is an infrared light emitting element or a visible light emitting element.   It has a light emitting element for displaying an operation state, and a photodetection device given in any 1 paragraph of Claims 1 thru / or 3, and uses the light emitting element as a light supply means of the photodetection device. Optical equipment.

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