JP2004309701A - Range-finding/photometric sensor and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure luminance in an area where a main subject exists in a photographic screen without being affected by infrared light, and to photograph the main subject with correct exposure without being affected by infrared light components. <P>SOLUTION: A 1st sensor array 5a constituted of photodiode having spectral sensitivity characteristics including the infrared light and a 2nd sensor array 5b constituted of photodiode having spectral sensitivity characteristics not including the infrared light are adjacently formed on an N type semiconductor substrate 40. And, the subject distance is detected with the 1st sensor array 5a, and the brightness of the subject is detected by the 2nd sensor array 5b based on the detection result of the subject distance. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a camera that performs correct exposure control in consideration of the distance and brightness of a main subject when performing photometry of a subject to be photographed, and a ranging photometry sensor that can be used in the camera.
[0002]
[Prior art]
In general, when shooting with a camera, in a backlight shooting scene in which a light source such as the sun is behind the main subject, a portion that becomes a shadow of the main subject is shot, so the main subject is crushed black. A phenomenon occurs. In order to prevent this, so-called daytime synchro photography has been performed, in which a shadow portion of a main subject is brightened by using reflected light or illumination light from a reflex board, or a strobe light is emitted during photography. .
[0003]
In this backlight determination, if the area occupied by the main subject with respect to the shooting screen is large, the determination can be made easily. However, in a shooting scene in which the area of the main subject is small, the luminance difference is small, so that it may not be determined that the subject is backlit.
[0004]
On the other hand, for example, an exposure control method using a focus detection unit (distance measurement unit) in combination with a photometry unit that performs photometry at the center and the periphery of a shooting screen is known (for example, see Patent Document 1).
[0005]
[Patent Document 1]
Patent No. 2934712
[0006]
[Problems to be solved by the invention]
According to Patent Literature 1 described above, an attempt is made to detect a backlight state of a main subject using a distance measuring sensor serving as a distance measuring unit. However, the S / N ratio of the distance measuring sensor is increased to improve the distance measuring accuracy. For improvement, it is preferable that the sensor has sensitivity to the infrared light component. However, when used as a photometric sensor, infrared light causes an error in the photometric value.
[0007]
Therefore, according to the present invention, the brightness of the area where the main subject is present on the photographing screen is correctly measured without being affected by the infrared light, and the backlight is determined by comparing this with the average luminance of the photographing screen. An object of the present invention is to provide a ranging photometry sensor and a camera capable of photographing a main subject with correct exposure without being affected by light components.
[0008]
[Means for Solving the Problems]
That is, the invention according to claim 1 is formed on a semiconductor substrate, and is formed on a first sensor having a spectral sensitivity characteristic including infrared light and on the same semiconductor substrate as the first sensor. A second sensor having a spectral sensitivity characteristic not including the infrared light, wherein the first sensor detects a subject distance, and the second sensor detects the subject distance. It is characterized in that the brightness of the subject is detected based on the result.
[0009]
With this configuration, it is possible to correctly detect the luminance of the area where the main subject exists on the photographing screen without being affected by the infrared light component.
[0010]
According to a second aspect of the present invention, in the distance measuring and photometric sensor according to the first aspect, the first and second sensors are formed adjacent to the semiconductor substrate. And
[0011]
With this configuration, it is possible to correctly detect the luminance of substantially the same portion of the photographing screen where the main subject exists without being affected by the infrared light component.
[0012]
According to the third aspect of the present invention, in the distance measuring and photometric sensor according to the first aspect, the first and second sensors are formed side by side in a depth direction of the semiconductor substrate. It is characterized by.
[0013]
With this configuration, it is possible to correctly detect the luminance of the region of the same portion where the main subject exists on the photographing screen without being affected by the infrared light component, and to further reduce the chip area. Can be.
[0014]
According to the invention described in claim 4, the first sensor having infrared sensitivity formed on the semiconductor substrate and the first sensor having infrared sensitivity are formed on the same semiconductor substrate as the first sensor. A second sensor having a lower infrared sensitivity than the first sensor, wherein the first sensor detects a subject distance, and the second sensor is configured to detect a subject distance based on a detection result of the first sensor. For the determined specific subject, the brightness of the subject is detected.
[0015]
With this configuration, it is possible to correctly detect the luminance of the area where the main subject exists on the photographing screen without being affected by the infrared light component.
[0016]
According to the fifth aspect of the present invention, a sensor for detecting an image signal of a subject present at a predetermined position in a photographing screen and an average photometric value representing an average brightness in the photographing screen are detected. Average photometric means, and determining means for comparing an output value of the sensor with the average photometric value to determine an exposure control amount at the time of photographing, wherein the sensor has a sensitivity in a visible light region. A first mode for performing conversion output and a second mode for performing photoelectric conversion output having sensitivity in a region including infrared light can be set.
[0017]
With this configuration, the brightness of the area where the main subject exists on the shooting screen is correctly measured without being affected by the infrared light, and the main subject is correctly exposed without being affected by the infrared light component. You can shoot.
[0018]
According to a sixth aspect of the present invention, in the camera according to the fifth aspect, the sensor forms the focus signal of the subject in the second mode.
[0019]
With this configuration, the brightness of the area where the main subject exists on the shooting screen is correctly measured without being affected by the infrared light, and the main subject is correctly exposed without being affected by the infrared light component. You can shoot.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
First, with reference to FIG. 6, the basic concept of backlight determination by the camera exposure control system to which the present invention is applied will be described.
[0022]
FIG. 6 shows the configuration of a camera exposure control system. 6, an exposure control system of the camera includes a photometric sensor 1, an average luminance calculating unit 2, a photometric backlight determining unit 3, a distance measuring sensor 5, a distance measuring unit 6, a subject selecting unit 7, A luminance calculating unit 8; a backlight determining unit 9; a strobe light emitting unit 10;
[0023]
The photometric sensor 1 calculates the luminance (photometric value) of the entire photographing screen, and its light receiving surface is divided into, for example, a peripheral photometric unit 1a and a central photometric unit 1b. The average luminance calculator 2 calculates the average luminance of the entire screen from the obtained photometric values. The photometric sensor 1 and the average luminance calculator 2 constitute an average photometric unit.
[0024]
In the photometric backlash determining section 3, the output of the peripheral photometric section 1a and the output of the central photometric section 1b of the divided photometric sensor 1 are compared to determine the backlight. The determination of the backlight state is effective when the main subject is located at the center of the shooting scene.
[0025]
The distance measuring sensor 5 performs a distance measuring operation on a plurality of distance measuring points in a shooting screen. This distance measuring sensor 5 is conceptually composed of a first sensor array 5a having a spectral sensitivity characteristic including infrared rays and a second sensor array 5b having a spectral sensitivity characteristic not including infrared rays. .
[0026]
The distance measurement calculation section 6 calculates the distance to the subject from the distance measurement data obtained by the distance measurement operation. Further, the subject selecting unit 7 selects, for example, a subject existing at the closest distance as a main subject from the plurality of distance results, and selects the location of the subject as a ranging point (hereinafter, referred to as a point) in the shooting screen. Is what you do.
[0027]
The luminance calculator 8 calculates the amount of light (luminance) incident on the point selected by the subject selector 7. Further, the backlight determining unit 9 determines whether or not the backlight is in a backlight state from the luminance of the selected point and the average luminance by a determination method described later.
[0028]
Further, the strobe light emitting section 10 emits auxiliary light at the time of backlighting, and the control section 11 controls the entire camera exposure control system including a function as a determining means and a strobe light emission control.
[0029]
Note that the above-described average luminance calculation section 2, photometric backlight determination section 3, distance measurement calculation section 6, subject selection section 7, luminance calculation section 8, backlight determination section 9, strobe light emission section 10, and control section 11 are actually implemented by the system. When constructed as, the arithmetic processing and control are realized by one microcomputer (CPU).
[0030]
In the exposure control system having such a configuration, an exposure operation is started by turning on a relay switch (not shown) of a camera, and first, the photometry sensor 1 performs photometry. Then, the average luminance of the entire screen is calculated by the average luminance calculation unit 2 from the obtained photometric values.
[0031]
Next, in a mode in which the distance measuring sensor 5 also has sensitivity to infrared rays (conceptually illustrated as the first sensor array 5a), distance measurement is sequentially performed on a plurality of points in the shooting screen. As a result, the distance measurement calculation unit 6 calculates the distance of each point to the subject using the obtained distance measurement data.
[0032]
The subject selecting unit 7 determines, for example, the closest one from the subject distances at each point as the point where the main subject exists, and selects the point to be focused. Further, the luminance calculator 8 monitors and obtains the luminance of the selected point. At this time, the distance measurement sensor 5 performs photometry independent of infrared light in the visible light detection mode (conceptually illustrated as the second sensor array 5b) by the mode switching function.
[0033]
Next, the backlight determination section 9 compares the average luminance of the entire screen with the luminance of the selected point to determine whether or not the shooting scene is in a backlight state. Here, if the average luminance of the entire screen is higher than the luminance of the selected point, it is determined that the surroundings are brighter than the main subject, that is, the backlight is in a backlight state. When the backlit shooting scene is shot, the strobe light is emitted from the strobe light emitting unit 10 in accordance with the ISO sensitivity of the film, the aperture value, and the subject distance.
[0034]
As described above, the backlight determination unit 9 makes a backlight determination based on the brightness of the selected point (main subject position) and the brightness of the entire screen, and enables appropriate exposure control. On the other hand, if the average luminance is smaller than the luminance at the point, it is determined that the main subject is not in a backlight state, and exposure control is appropriately performed.
[0035]
FIG. 7 is a diagram showing a specific configuration example of an electronic circuit system of a camera as a first embodiment of the present invention to which the above-described exposure control system is applied.
[0036]
The camera in this embodiment is an example applied to a so-called digital camera in which a subject image is converted into image data by a photoelectric conversion element, and various image processes are performed and recorded.
[0037]
This camera has a distance measuring unit 18 mainly composed of a pair of light receiving lenses 16a and 16b and a pair of sensor arrays 17a and 17b arranged apart from a subject 15 by a base line length B, and an A / D converter. Unit 19, an AE lens 20, a split type AE sensor 21a, 21b for receiving light condensed by the AE lens 20, an AE circuit 22, and a photographing lens (zoom lens) 24 for forming a subject image. , An image sensor 25 composed of a CCD or the like, an image processing unit 26, a recording unit 27, a lens driving unit (LD) 28, a zoom driving mechanism 29, a strobe driving unit 30, a strobe light projecting unit 31 And an operation control unit (CPU) 33 and a switch input unit 34.
[0038]
The distance measuring section 18 measures the distance L to the subject 15. In the distance measuring section 18, an image of the subject 15 is received by a pair of sensor arrays 17a and 17b via a pair of light receiving lenses 16a and 16b. Then, subject image signals are generated by photoelectric conversion in the sensor arrays 17a and 17b.
[0039]
In the A / D converter 19, the subject image signal from the distance measuring unit 18 is A / D converted, and a digital image signal is output to the CPU 33.
[0040]
The light condensed by the AE lens 20 for exposure is guided to divided AE sensors 21a and 21b for measuring the center and the periphery of the screen. With respect to the light guided to the AE sensors 21a and 21b, the brightness in the photographing screen is measured by an AE circuit 22 including a logarithmic compression circuit and the like.
[0041]
The image of the subject 15 is formed on the image sensor 25 by the photographing lens 24. In the image pickup device 25, image data based on the formed subject image is generated. Then, the image data obtained by the image pickup device 25 is output to the image processing unit 26 and subjected to image processing such as γ conversion and image compression. Further, the image data subjected to the image processing is recorded in the recording unit 27.
[0042]
The photographing lens 24 is focused by driving the lens driving unit 28. Further, a mirror frame (not shown) in the photographing lens 24 is moved by the zoom driving mechanism 29 to change the photographing angle of view.
[0043]
The CPU 33 controls the entire camera, and comprises a one-chip microcomputer or the like. The switch input unit 34 includes a switch for starting a predetermined sequence in the CPU 33 by an operation of the photographer.
[0044]
Further, the strobe light projecting section 31 is for projecting auxiliary illumination light to the subject 15, and light emission is controlled by driving control of the strobe driving section 30.
[0045]
In the components of this camera, only the members relating to the gist of the embodiment are described, and other components that the ordinary camera has are assumed to have the same The description is omitted.
[0046]
In the CPU 33, the light is condensed by a pair of light receiving lenses 16 a and 16 b disposed apart from each other by a base line length B of the distance measuring unit 18, photoelectrically converted by a pair of sensor arrays 17 a and 17 b, and further converted by an A / D converter 19. The pair of A / D converted digital image signals are compared. Thus, a relative position difference x between the image input positions is obtained. At this time, in the sensor arrays 17a and 17b, image detection is performed in a mode having sensitivity in the infrared region where the S / N ratio is good. In this mode, an auxiliary light such as an infrared light emitting diode, which is not dazzling to the eyes of a person, can be used effectively, so that a dazzling image can be shot even in a dark place.
[0047]
This varies according to the relationship x = B · f / L depending on the subject distance L as shown in FIG. 7, the focal length f of the light receiving lenses 16a and 16b, and the base line length B. The alignment distance L can be calculated. In this case, since the sensor arrays 17a and 17b extend in the horizontal direction, the area 37a is monitored when a shooting scene as shown in FIG. 8 is aimed. As shown in FIG. 9A, this area 37a is divided into seven blocks, and the above-described detection is performed using the image signal of each block, thereby measuring seven points in the screen. Distance becomes possible. Of the seven distance measurement results obtained, for example, the one that indicates the closest distance is the main subject distance.
[0048]
When the photographing lens 24 is a zoom lens, if the angle of view is shifted to the telephoto side, only the photographing area 38T in the screen can be photographed in the photographing scene shown in FIG. At this time, if the distance measurement area remains in the area 37a, the distance is measured to an object outside the screen. Therefore, at the time of telephoto, the multi-point AF (multi-AF) of seven points is performed in the narrowed seven regions as shown in FIG.
[0049]
The brightness of the entire screen is measured by the AE circuit 22 and the AE sensors 21a and 21b, and exposure control is performed by the CPU 33 based on the photometric result. In the AE sensors 21a and 21b, the output of the AE sensor 21a, that is, the area (telephoto) 36 shown in FIG. 8 is selected in telephoto according to a change in the angle of view due to zooming of the photographing lens 24. Photometry is performed. On the other hand, at the time of wide angle, the sum of the outputs of the AE sensor 21a and the AE sensor 21b, that is, the area (at the time of wide angle) 35 is selected and photometry is performed.
[0050]
In addition, as shown in FIG. 9C, each of the points for distance measurement shown in FIG. 9A and FIG. 9B is divided into strip-shaped pixels arranged in a plurality of rows. Consists of This is because each pixel outputs data according to the shadow of the image, so that image data as shown in FIG. 9D is obtained. When these are averaged, an average luminance of each point is obtained.
[0051]
As described above, the position of the main main subject is detected by the multi-AF, and the luminance at that position is further obtained. Therefore, according to the flowchart shown in FIG. 10, it is possible to perform shooting by exposure control with emphasis on the main subject. However, when calculating the luminance, the infrared light component causes an error, so that the image detection is performed in the characteristic visible light detection mode.
[0052]
First, in step S1, the zoom position of the taking lens 24 is determined. Next, in step S2, it is determined from the obtained zoom position whether or not the photographing lens 24 is on the wide angle side.
[0053]
In this determination, if the angle is on the wide angle side, the angle of view becomes 38W shown in FIG. 8, and the flow shifts to step S3 to select the photometry range 35 and the distance measurement range 37a. On the other hand, if it is not on the wide-angle side, that is, if it is on the telephoto side, the angle of view becomes 38T shown in FIG. 8, and the process proceeds to step S4, where the photometry range 36 and the distance measurement range 37b are selected.
[0054]
Next, in step S5, ranging is performed in the ranging range selected in this manner. In this distance measuring step, it is assumed that the distance measuring section 18 has been switched to the mode of image detection by sensitivity including infrared light by the CPU 33. From this distance measurement result, in step S6, a point (distance measurement point) indicating the closest distance where the main subject exists is determined as the selected point.
[0055]
In step S7, in order to detect the brightness of the image output at the selected point, the spectral sensitivity of the distance measuring sensor is switched to the visible light mode, and the image signal obtained by integrating the photocurrent is detected again. (See FIG. 4D). From the brightness of the main subject obtained in this way, in step S8, the photometric average value SP _Ave Is calculated.
[0056]
Subsequently, in step S9, photometry in the photometry range (photographing screen) by the AE sensor selected in step S4 is performed. Further, in step S10, the photometric average value BV, which is the average of the outputs obtained by this photometry, _Ave Is calculated.
[0057]
In step S11, the guide number of the strobe is calculated based on the main subject distance obtained in step S6, the ISO sensitivity of the film, and the zoom position information obtained in step S1, and the strobe light is emitted. Is determined to reach the main subject.
[0058]
If it is determined that the strobe light reaches the main subject, the process proceeds to step S12, and the average photometric value BV _Ave Is the predetermined position BV _O It is determined whether or not this is the case. That is, the obtained photometric average value SP of the main subject is obtained. _Ave Is determined using the average photometric value. This is because the linearity (dynamic range) of photometry is limited because the output of the distance measurement sensor does not pass through a logarithmic compression circuit. Here, the average photometric value BV _Ave Is the predetermined position BV _O It is determined whether or not this is the case.
[0059]
In the determination in step S12, the photometric average value BV _Ave Is larger, the main subject photometry average value SP _Ave Is trusted. In this case, the process proceeds to step S13, and the main subject photometric average value SP _Ave And photometric average value BV _Ave Is compared with And the photometric average value BV _Ave Is larger, that is, whether it is backlight or not.
[0060]
On the other hand, if the strobe light does not reach the main subject in the determination in step S11, the average photometric value BV is determined in step S12. _Ave Is the predetermined value BV _O If the value is less than or less than the photometric average value BV _Ave Is the main subject photometry average value SP _Ave If it is smaller, the process proceeds to step S14.
[0061]
In this step S14, the main subject photometric average value SP _Ave Average photometric value BV without considering _Ave Exposure control is performed. Thus, a series of sequences is completed.
[0062]
In step S13, the main subject photometry average value SP _Ave Than the photometric average BV _Ave Is determined to be larger, that is, when the shooting scene is in a backlight state where the surroundings are brighter than the main subject, or when the shooting scene requires strobe light, the auxiliary light by strobe light emission is used. Exposure is performed while supplementing with. Thus, a series of sequences is completed.
[0063]
As described above, according to the present embodiment, a point for focusing in the shooting screen and a point for exposure matching are matched, and a photometric value (luminance) is compared to determine backlight. For the photographer, the backlight is determined by a simple operation of only pressing the release button, and the exposure suitable for the shooting scene is performed, so that a photograph with beautiful focus and exposure can be taken. At this time, the distance to the main subject is detected, and when the distance is specified, image detection is performed using spectral sensitivity including infrared light having a good S / N ratio. Since image detection using only components is performed, highly accurate spot photometry can be performed.
[0064]
Also, since consideration is given to whether or not the strobe light reaches the main subject properly, it is possible to prevent unnecessary battery consumption due to strobe light emission.
[0065]
Next, the configuration of the distance measuring sensor having the function of switching the spectral sensitivity used in the above embodiment will be described in more detail.
[0066]
FIG. 1 shows a first embodiment of the present invention, and is a cross-sectional view of a semiconductor chip of a sensor for switching spectral sensitivity, which is a sensor in which a photometric sensor array is adjacent to a distance measuring sensor array.
[0067]
In this embodiment, two light receiving sections having different characteristics are not adjacent to each other, but are formed on the same semiconductor substrate so that substantially the same subject portion can be detected.
[0068]
In the figure, a first sensor array (first sensor) 5a is a pixel unit having sensitivity to infrared light as well as visible light, and a second sensor array (second sensor) 5b is This is a pixel portion having sensitivity to visible light.
[0069]
The first sensor array 5a includes a P-type diffusion layer (P-type) on the surface of an N-type semiconductor substrate (N-sub) 40. ⁺ ) 42 are formed. In the second sensor array 5b, a P-type semiconductor layer (Pwell) 41 is formed on an N-type semiconductor substrate 40, and an N-type diffusion layer (N-well) is formed on the surface of the substrate in the P-type semiconductor layer 41. ⁺ ) 43 are formed.
[0070]
Since the first sensor array 5a uses the N-type semiconductor substrate 40 itself on the N-side of the PN junction, it is possible to extract even the photoelectric conversion signal generated at the depth of the N-type semiconductor substrate 40. Since light having a long wavelength (infrared component) of the light reaches the depth of the substrate, the output of the first sensor array 5a has a spectral sensitivity ranging from visible light to infrared light.
[0071]
On the other hand, in the second sensor array 5b, a P-type semiconductor layer 41 is formed in an N-type semiconductor substrate 40, an N-type diffusion layer 43 is further formed therein, and the PN junction is used as a photodiode. are doing. Therefore, an output signal of a relatively shallow portion (only visible light) can be taken out, and a component generated in a deep portion which is hardly dependent on an infrared light component is connected to the P-type semiconductor layer 41 by grounding. By doing so, it is removed from the ground line so that the visible light signal is not affected. In the drawing, reference numeral 44 denotes a voltage value V _DD Power supply.
[0072]
Next, the relationship between the wavelength and the output will be described in more detail with reference to FIG.
[0073]
FIG. 2 is a characteristic diagram showing the relationship between the wavelength of incident light and the absorption depth in silicon (semiconductor substrate).
[0074]
If the incident light has a long wavelength, it penetrates deep into the substrate, and if it has a short wavelength, it penetrates only deep into the substrate. Then, the P-type semiconductor layer (Pwell) 41 and the N-type diffusion layer (N ⁺ In the photodiode between (1) and (2), carriers generated in a deep portion of the substrate are absorbed by a PN junction formed by the Pwell 41 and the N-type semiconductor substrate (N-sub) 40, and thus are generated in a shallow region of the substrate. Only the performed carriers are detected. That is, a photodiode having greater sensitivity to light of a short wavelength is configured.
[0075]
On the other hand, the P-type diffusion layer (P) formed in the first sensor array 5a ⁺ ) 42 and the photodiode of the N-type semiconductor substrate (N-sub) 40, the carriers generated deep in the substrate are also detected at the same time, so that a photodiode having sensitivity up to a long wavelength is formed.
[0076]
FIG. 3 is a characteristic diagram of photodiodes having different spectral sensitivities. The difference in the depth at which light is detected by the two types of photodiodes causes a difference in spectral sensitivity.
[0077]
Next, a photoelectric conversion signal readout circuit of a distance measuring image sensor having a sensor having such a configuration will be described with reference to the circuit configuration diagram of FIG.
[0078]
As shown in FIG. 1, here, photodiodes having different light detection depths are used. A readout circuit is formed in each of the photodiodes 51 and 67 so that a signal is extracted. That is, the photodiode 51 using only visible light is provided with an N-type read circuit 81a based on the NMOS transistor 54. On the other hand, a photodiode 67 including visible light and infrared light is provided with a P-type read circuit 81b based on a PMOS transistor 69.
[0079]
First, an N-type read circuit will be described.
[0080]
In FIG. 4, the source of the N-type MOS transistor 54 is grounded, and the load transistor 53 and the capacitor 55 are connected to the drain, thereby forming a grounded-source amplifier circuit. The photodiode 51 is connected to the input terminal of the common-source amplifier circuit, that is, the gate of the N-type MOS transistor 54, and the output terminal of the common-source amplifier circuit, that is, the drain of the N-type MOS transistor 54 is connected to the input terminal (N A capacitor 55 is connected to the gate of the N-type MOS transistor 54 for feedback, and an N-type resetting MOS transistor 53 for setting the initial potential of the gate of the N-type MOS transistor 54 is connected in parallel with the capacitor 55. .
[0081]
This configuration is used as a basic cell (pixel), and when the basic cells are arranged one-dimensionally or two-dimensionally, a selection transistor 63 driven by a shift register pulse for selecting a pixel to be read out has an N. It is connected to the drain of the type MOS transistor 54 (node 56). The configuration is such that the drain voltage of the N-type MOS transistor 54 appears in the CDS circuit 64 when the selection transistor 63 is turned on. The CDS circuit 64 can obtain only a signal component accompanying light.
[0082]
The load of the common-source amplifier circuit is configured as an active load by a P-type MOS transistor 59. A bias voltage and a power supply voltage are applied to the gate 58 and the source 57 of the load P-type MOS transistor 59, respectively. Incidentally, 52 and 62 are a reset terminal and a selection terminal, respectively.
[0083]
Next, a P-type read circuit will be described.
[0084]
The configuration of the P-type read circuit is basically a configuration in which the N-type MOS transistor of the above-described N-type read circuit is configured by a P-type MOS transistor and the polarity is inverted. That is, the source of the P-type MOS transistor 69 is grounded, and the load transistor 72 and the capacitor 70 are connected to the drain, thereby forming a grounded-source amplifier circuit. The photodiode 67 is connected to the input terminal of the common-source amplifier circuit, that is, the gate of the P-type MOS transistor 69, and the output terminal of the common-source amplifier circuit, that is, the drain of the P-type MOS transistor 69 is connected to the input terminal (P A capacitor 70 is connected to the gate of the P-type MOS transistor 69 to apply feedback, and a reset P-type MOS transistor 72 for setting the initial potential of the gate of the P-type MOS transistor 69 is connected in parallel with the capacitor 70. .
[0085]
With this configuration as a basic cell (pixel), when the basic cells are arranged one-dimensionally or two-dimensionally, a selection transistor 78 driven by a shift register pulse for selecting a pixel to be read is provided with a P transistor. It is connected to the drain of the type MOS transistor 69 (node 73). The configuration is such that the drain voltage of the P-type MOS transistor 69 appears in the CDS circuit 79 when the selection transistor 78 is turned on. The CDS circuit 79 can obtain only a signal component accompanying light.
[0086]
The load of the common-source amplifier circuit is configured as an active load by an N-type MOS transistor 75. A bias voltage is applied to the gate 74 of the load N-type MOS transistor 75. 66, 71 and 77 are a power supply voltage terminal, a reset terminal and a selection terminal, respectively.
[0087]
Whether the N-type sensor or the P-type sensor is used is determined by the CPU switching and selecting the analog switch 80 for mode switching, and detecting an output having different spectral sensitivity and characteristics from the output terminal. Can be.
[0088]
Here, the source ground readout method will be described.
[0089]
Taking the N-type read circuit as an example, the output signal is expressed by the following equation.
V _OUT = V _GS + I _P T / {(1 + 1 / G) Ct + 1 / G · Cd} (1)
Where V _GS Is a gate-source voltage of the N-type MOS transistor 54 at the time of reset, and this is also a drain voltage at the time of reset. G is the gain of the common-source amplifier circuit, Ct is the capacitance value of the feedback capacitor 55, Cd is the junction capacitance value of the photodiode 51, and I is _P , T are the photocurrent and the integration time.
[0090]
As can be seen from the above equation (1), the effect of the junction capacitance Cd of the photodiode 51 can be suppressed by increasing the gain G of the common-source amplifier circuit by increasing the output signal due to the photoelectric conversion. As a result, the capacitance value Ct of the feedback capacitor 55 is reduced, so that the output voltage V _OUT , Ie, the sensitivity can be increased.
[0091]
Next, the pulse timing of the read circuit will be described with reference to FIG.
[0092]
FIG. 5A is a timing chart illustrating a method for driving the N-type read circuit.
[0093]
The period T1 is a reset period. Here, the selection transistor 63 and the reset transistor 53 are turned on, and the potential of the photodiode 51 is set to the initial potential. Then, in the reset level reading period of the period T2, the reset transistor 53 is turned off and the reset level is read while the selection transistor 63 is kept on.
[0094]
Next, in a period T3, both the reset transistor 52 and the selection transistor 63 are turned off to be in an accumulation state. Further, in a period T4, the signal level is read.
[0095]
Thus, a signal can be read as a voltage change from the reset level by the CDS operation.
[0096]
Actually, a signal is read out one-dimensionally on a line while repeating a selection operation by a shift register or the like.
[0097]
FIG. 5B is a timing chart illustrating a driving method of the P-type read circuit. The operation of the P-type readout circuit is the same as that of the above-described example of the N-type readout circuit, and a description thereof will not be repeated.
[0098]
(Second embodiment)
Next, as a second embodiment of the present invention, another configuration example of the infrared, visible, and visible sensitivity switching sensor will be described with reference to FIG.
[0099]
Note that, in the second embodiment, the same parts as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0100]
FIG. 11A shows the second embodiment, and is a configuration diagram showing an example in which photodiodes of a type in which photodiodes are formed vertically in a semiconductor substrate realize different spectral sensitivities.
[0101]
As shown in FIG. 11A, this sensor differs from the sensor of the first embodiment described above in that two PN junctions are formed in the depth direction of the N-type semiconductor substrate, and It is configured as a photodiode. That is, a photodiode (second sensor array) 5b for visible light is formed at a shallow position under the same light receiving surface, and a photodiode (first sensor array) 5a for infrared light is formed at a deep position. Is formed.
[0102]
The outputs of the photodiodes 5a and 5b are output from the N-type read circuit 81a and the P-type read circuit 81b via the analog switch 80, respectively. As described above, a signal is read out to each of the photodiodes 51 and 67 using the above-described reading circuit.
[0103]
FIG. 11B is a diagram illustrating a circuit configuration of the sensor having the configuration illustrated in FIG. A short-wavelength output is obtained on the N-type readout circuit 81a side, and a long-wavelength output is obtained on the P-type readout circuit 81b.
[0104]
With the photodiode having the vertical structure, it is possible to realize the same pixel configuration as in the first embodiment of the horizontal structure described above. In this case, the driving method is the same as that of the above-described readout circuit of the first embodiment, and thus the description is omitted.
[0105]
The second embodiment is different from the adjacent type of the first embodiment described above, and has the merit that the same portion of the object can be measured and the chip area can be reduced.
[0106]
(Third embodiment)
Next, a third embodiment of the present invention will be described.
[0107]
Note that, in the second embodiment, the same parts as those in the above-described first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0108]
In the third embodiment, similarly to the above-described second embodiment, a sensor capable of switching spectral sensitivity is formed by stacking photodiodes in the depth direction of the substrate.
[0109]
FIG. 12A shows the third embodiment, and is a configuration diagram showing an example in which photodiodes of a type in which photodiodes are formed vertically in a semiconductor substrate realize different spectral sensitivities.
[0110]
As shown in FIG. 12A, this sensor is different from the sensor of the above-described second embodiment in that an N-type semiconductor substrate is replaced with a P-type semiconductor substrate and below an N-type diffusion layer. The structure of the portion excluding the P-type diffusion layer is different. In addition, the short wavelength output is obtained on the N-type readout circuit 81a side, and the long wavelength output is obtained on the N-type readout circuit 82 side.
[0111]
As shown in FIG. 12B, the configuration of the N-type readout circuit 82 is basically the same as that of the N-type readout circuit 81a, except that the photodiodes 51 are 67a and 67b. The components are simply replaced by the reference numerals 53, 54, 55, 56, 59, 63 with 83, 84, 85, 86, 87, 88 respectively. Other configurations and operations are the same as those of the above-described first and second embodiments, and thus illustration and description are omitted.
[0112]
According to the third embodiment, the manufacturing process can be further simplified by a portion that is further removed.
[0113]
【The invention's effect】
As described above, according to the present invention, the brightness of the area where the main subject is present on the shooting screen is correctly measured without being affected by the infrared light, and the backlight determination is performed by comparing this with the average brightness of the shooting screen. Accordingly, it is possible to provide a ranging photometry sensor and a camera capable of photographing a main subject with a correct exposure without being affected by an infrared light component.
[0114]
According to the first aspect of the present invention, it is possible to correctly detect the luminance of the region where the main subject exists on the photographing screen without being affected by the infrared light component.
[0115]
According to the second aspect of the present invention, it is possible to correctly detect the luminance of substantially the same part of the area where the main subject exists on the photographing screen without being affected by the infrared light component.
[0116]
According to the third aspect of the present invention, it is possible to correctly detect the luminance of the region of the same portion where the main subject exists on the photographing screen without being affected by the infrared light component, and to further reduce the chip area. Can be smaller.
[0117]
According to the fourth aspect of the present invention, it is possible to correctly detect the luminance of the area where the main subject exists on the photographing screen without being affected by the infrared light component.
[0118]
According to the fifth aspect of the present invention, the luminance of the area where the main subject is present on the photographing screen is correctly measured without being affected by the infrared light, and the luminance of the main area is not affected by the infrared light component. The subject can be photographed with the correct exposure.
[0119]
According to the invention described in claim 6, the brightness of the area where the main subject exists on the photographing screen is correctly measured without being affected by the infrared light, and the brightness of the main subject is determined without being affected by the infrared light component. You can shoot with the correct exposure.
[Brief description of the drawings]
FIG. 1 shows a first embodiment of the present invention, and is a cross-sectional view of a semiconductor chip of a sensor for switching spectral sensitivity, which is a sensor in which a photometric sensor array is adjacent to a distance measuring sensor array.
FIG. 2 is a characteristic diagram showing a relationship between a wavelength of incident light and an absorption depth in silicon (semiconductor substrate).
FIG. 3 is a characteristic diagram of photodiodes having different spectral sensitivities.
FIG. 4 is a diagram showing a configuration of a photoelectric conversion signal readout circuit of the distance measuring image sensor having the configuration of FIG. 1;
FIGS. 5A and 5B are timing charts for explaining a pulse timing of a reading circuit, in which FIG. 5A is a timing chart for explaining a driving method of an N-type reading circuit, and FIG. .
FIG. 6 is a diagram showing a configuration of a camera exposure control system.
FIG. 7 is a diagram showing a specific configuration example of an electronic circuit system of a camera as a first embodiment of the present invention to which the exposure control system of FIG. 6 is applied.
FIG. 8 is a diagram illustrating a relationship between a shooting scene, a shooting area, and a photometry area.
9A is a diagram showing an example of divided blocks of an area 37a in FIG. 8, FIG. 9B is a diagram showing an example of multi-AF at telephoto, and FIG. 9C is a diagram of FIG. FIG. 9D is a diagram showing points for distance measurement of the block, and FIG. 9D is a diagram showing image data obtained from the pixel of FIG.
FIG. 10 is a flowchart illustrating an operation of distance measurement and photometry in the first embodiment of the present invention.
FIG. 11A shows a second embodiment, and is a configuration diagram showing an example of realizing different spectral sensitivities with photodiodes of a type in which photodiodes are formed vertically in a semiconductor substrate, and FIG. 2) is a diagram showing a circuit configuration of the sensor having the configuration shown in FIG.
FIG. 12A shows a third embodiment, and is a configuration diagram showing an example in which photodiodes of a type in which photodiodes are vertically formed in a semiconductor substrate realize different spectral sensitivities; FIG. 2B is a diagram illustrating a circuit configuration of the sensor having the configuration illustrated in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photometric sensor, 1a ... Perimeter photometric section, 1b ... Central photometric section, 2 ... Average brightness calculation section, 3 ... Photometric backlight determination section, 5 ... Distance measuring sensor, 5a ... First sensor array (photodiode), 5b ... A second sensor array (photodiode), 6) a distance measuring calculator, 7) a subject selector, 8) a luminance calculator, 9) a backlight determining unit, 10) a strobe light emitting unit, 11) a controller, 15 ... a subject , 16a, 16b: light receiving lens, 17a, 17b: sensor array, 18: distance measuring unit, 20: AE lens, 21a, 21b: AE sensor, 40: N-type semiconductor substrate (N-sub), 41: P-type semiconductor Layer (Pwell), 42 ... P-type diffusion layer (P ⁺ ), 43... N-type diffusion layer (N ⁺ ).

Claims (6)

A first sensor formed on a semiconductor substrate and having a spectral sensitivity characteristic including infrared light;
A second sensor formed on the same semiconductor substrate as the first sensor and having a spectral sensitivity characteristic not including the infrared light;
With
The first sensor detects a subject distance, and the second sensor detects the brightness of the subject based on a result of detection by the first sensor. The sensor according to claim 1, wherein the first and second sensors are formed adjacent to the semiconductor substrate. 2. The sensor according to claim 1, wherein the first and second sensors are formed side by side in a depth direction of the semiconductor substrate. 3. A first sensor formed on a semiconductor substrate and having infrared sensitivity;
A second sensor which is formed on the same semiconductor substrate as the first sensor and has a lower infrared sensitivity than the first sensor;
With
The first sensor detects a subject distance, and the second sensor detects the brightness of the subject for the specific subject determined based on the detection result of the first sensor. Sensor for distance measurement and photometry. A sensor for detecting an image signal of a subject present at a predetermined position in the shooting screen,
Average photometric means for detecting an average photometric value representing an average brightness in the shooting screen,
Determining means for comparing the output value of the sensor and the average photometric value to determine an exposure control amount at the time of shooting;
With
The sensor is capable of setting a first mode for performing a photoelectric conversion output having sensitivity in a visible light region and a second mode for performing a photoelectric conversion output having sensitivity in a region including infrared light. Camera. 6. The camera according to claim 5, wherein the sensor forms a focus signal of the subject in the second mode.

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