JPH02102582A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To enable the accurate correction of the focal deviation due to the spectral distribution difference of a subject by a method wherein a photodetector is provided to detect the spectral distribution of the subject. CONSTITUTION:A reset gate is provided between an N<+>-type floating junction layer 4 and an N<+>-type reset drain layer 5, and a reset pulse phiR is applied to the reset gate to set the potential of the layer 4 to a reset potential VRS of a power source connected to the layer 5. When a photodetector is exposed to light for a certain time, charges are accumulated in a photodiode N-type layer 3 corresponding to the exposure time and the light intensity of blue, green, and red light. When the accumulated charges are transferred to the layer 4 by applying a transfer pulse phiT to the transfer gate provided between the layers 3 and 4, the potential of the layer 4 is made to vary corresponding to the quantity of the transferred charges, the potential variation is outputted through the intermediary of an output detection circuit 10. By this setup, it can be accurately judged independent of a spectral distribution if a focal point is right or not.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a photoelectric conversion device, particularly a semiconductor photoelectric conversion device used in an autofocus camera, etc., which has a function of detecting the spectral distribution emitted by a subject. The present invention relates to a photoelectric conversion device having:

[Prior Art] An autofocus CCD is known as a photoelectric conversion device used in a conventional autofocus camera, and an autofocus function using this will be explained with reference to the drawings. FIG. 3 is a principle diagram of a device for detecting the autofocus state of a camera, in which FIG. 3(a) shows the in-focus state, FIG. 3(b) shows the front focus state, and FIG.
) respectively represent the rear focus state. In the figure, 101 is a subject, 102 is a photographic lens, 103 is a photosensitive plate surface, 104 is a separator lens that divides the image taken by the photographic lens into two, and 105 is a measurement of the distance between the two divided images. It is a CCD for

As shown in the figure, since the image formation position on the CCD surface differs depending on the focusing state, the focusing state can be determined by measuring the distance V@ between the two images. now,
The distance between the images in the in-focus state is dO1, and the distance between the images in the front-focus state and the rear-focus state are d, d, respectively. Since there is a relationship of d2 > do > d+, the focus is adjusted by the autofocus mechanism. In order to do this, it is sufficient to measure the inter-image distance, compare this measured value with the distance 11 d o in the in-focus state, and automatically operate the photographing lens mechanism through the control mechanism so as to match this value.

[Problems to be Solved by the Invention] In the conventional example described above, even if the distance to the subject is the same and the condition of the photographing lens is the same, the distance between images detected by the CCD differs depending on the spectral distribution of the subject. It's coming. In other words, if the spectral distribution of the object is closer to short wavelengths due to the difference in refractive index depending on the wavelength of the separator lens, the inter-image distance will not be dO even if the image is placed temporarily and in focus. become smaller. On the other hand, even if the inter-image distance is cto, if the spectral distribution is closer to the short wavelength side or the long wavelength side, it is out of focus. Therefore, the spectral distribution of the subject must be accurately understood. Even if the distance between images is measured, the focusing state cannot be determined correctly.

Therefore, an object of the present invention is to provide a photoelectric conversion device that can accurately determine the focusing state regardless of the spectral distribution.

[Means for Solving the Problems] A photoelectric conversion device according to the present invention is a photoelectric conversion device that measures the distance between two images formed in a semiconductor substrate and formed on the semiconductor surface. At least two light-receiving elements having mutually different spectral sensitivity characteristics are further formed in the semiconductor substrate on which the conversion device is formed, in order to measure the spectral distribution of the incident light that forms the image. .

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a light receiving element portion of an embodiment of the present invention. As shown in the figure, three sets of photodiode N-type layer 3, N1-type floating junction layer 4, and N+ type lit drain layer 5 are formed in P-type semiconductor substrate 1, and these are P-conducting. separated by a mold channel stop 2. A transfer gate is provided between each photodiode N type layer 3 and each N+ type floating junction layer 4, and each N+ type floating junction layer 4 is provided with a transfer gate.
A reset gate is provided between the type floating junction layer 4 and each N" type reset drain layer 5. On each photodiode N type layer 3, a reset gate is provided.
A blue color filter 7, a green color filter 8, and a red color filter 9 are formed, respectively. Furthermore, an output detection circuit 10 is connected to each N+ type floating junction layer 4 in order to detect the amount of photoelectrically converted charge.

Focusing using this light receiving element is performed as follows. First, a reset pulse φ is applied to the reset gate to reset the potential of the floating junction layer 4 to the reset potential VF1 of the power supply to which the drain layer 5 is connected.
Fixed to s. When the light-receiving element is exposed to light for a certain period of time, charges corresponding to the exposure time and the light intensity of each color are accumulated in the photodiode N-type layer 3. This accumulated charge is transferred to the floating junction layer 4 by applying a transfer pulse φd to the transfer gate. The potential of the floating junction layer 4 varies depending on the amount of charge, and this potential variation is caused by the output detection circuit 10
Output via . Since the outputs V, , V, and V range of each output detection circuit 10 indicate the intensity of blue, green, and red component light, now, VB > VQ, VR
If so, then in this case, the spectral distribution of this subject will have a maximum in the blue region. Therefore, in this case, the inter-image distance ud at the focused point in FIG. , do−Δ
d, and focus is adjusted to match this value.

FIG. 2 is a longitudinal sectional view of a light receiving element according to another embodiment of the present invention. In FIG. 2, parts that are the same as those in FIG. 1 are given the same numbers, so redundant explanation will be omitted. In FIG. 2, 3a is an N-type layer of a shallow PN photodiode that has a sensitivity peak on the short wavelength side, and 6 is an MOS capacitor type layer to which a store gate signal φsT is applied and has a sensitivity peak on a medium wavelength side. The polycrystalline silicon gate of the photodiode, 3b, is an N-type layer of a deep PN photodiode with a peak sensitivity at long wavelengths. Even if this light receiving element is used, accurate focusing can be performed as in the example shown in FIG.

In the above embodiment, three photodiodes were used, but the present invention is not limited to this, and two to four or more photodiodes may be used. When using multiple photodiodes, the sensitivity peak should be in blue or red, and if the output of one of the photodiodes is greater and the output level exceeds a certain value, the peak of sensitivity will be detected. The distance between images at focus is corrected. On the other hand, when four or more photodiodes are used, the peak of the spectral distribution of the object can be measured more precisely, so more accurate focusing is possible.

[Effects of the Invention] As explained above, in the present invention, a photoelectric conversion device for autofocus is provided with a light receiving element for detecting the spectral distribution of the subject. It is possible to accurately correct the out-of-focus caused by the difference in the light-receiving element using the output of the light-receiving element. Moreover, the present invention
Since the light-receiving element that measures the spectral distribution is formed on the same semiconductor substrate as the photoelectric conversion element that measures the inter-image distance, even if the number of elements increases, the size of the photoelectric conversion device does not increase significantly. It is convenient to implement inside the camera.

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views of a light-receiving element portion of an embodiment of the present invention, and FIG. 3 is a diagram illustrating the principle of an autofocus mechanism. 1...P-type semiconductor substrate, 2...Channel stopper 1.3.3a, 3b...Photodiode N-type layer, 4...N+ type Mouth loading junk 5 6...Polycrystalline silicon gate, 7...
・Blue color filter, 8... Green color filter 9... Red color filter 5
10... Output detection circuit, 101...
...Subject, 102...Photographing lens, 10
3...Sensitive plate surface, 104...Separator lens, 105...COD for autofocus.

Claims (1)

[Claims] 2 formed within a semiconductor substrate and imaged on the semiconductor substrate surface.
In a photoelectric conversion device that measures the distance between two images, a semiconductor substrate on which the photoelectric conversion device is formed includes light receiving elements having mutually different spectral sensitivity characteristics in order to measure the spectral distribution of the incident light that forms the image. A photoelectric conversion device characterized in that at least two of these are formed.