Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Reexamination Certificate
1999-04-14
2001-02-06
Evans, F. L. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
C250S201800, C396S097000
Reexamination Certificate
active
06184511
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor integrated circuit and photoelectric conversion apparatus for of converting an optical signal into an electrical signal.
2. Related Background Art
A semiconductor component such as a semiconductor integrated circuit in a photoelectric conversion apparatus has a circuit for detecting changes in ambient temperature which the apparatus uses to correct operation characteristics in accordance with changes in the temperature. For example, ambient temperature changes are detected by a method as shown in
FIG. 1
, in a device such as an autofocus sensor (to be referred to as an AF sensor hereinafter) which must perform high-precision processing over a large temperature change range from −20° C. to +60° C.
FIG. 1
is a block diagram showing an autofocus-associated part of a conventional camera.
FIG. 1
schematically shows a camera unit
601
. The camera unit
601
comprises a thermometer
602
arranged outside a package
605
, an AF sensor IC
604
having a photoelectric conversion element
608
, a thermometer circuit
603
mounted on the package
605
of the AF sensor IC
604
, a lens
610
and a secondary image formation lens
606
for receiving an incident optical signal from a subject image, a microcomputer
607
for processing an image signal, and a lens control unit
609
for controlling the position of the lens
610
.
The camera unit
601
receives a subject image signal via the secondary image formation lens
606
, forms images A and B corresponding to right and left lenses constituting the secondary image formation lens
606
on the photoelectric conversion element
608
of the AF sensor IC, performs correlation calculation for the subject image signal by the microcomputer
607
, and controls the focal point of the camera lens
610
by operation of the lens control unit
609
to calculate the distance from the lens
610
to the subject to be photographed.
The influence of changes in ambient temperature on the camera unit
601
includes changes in characteristics of the secondary image formation lens
606
upon thermal expansion/shrinkage. If the characteristics of the secondary image formation lens
606
change depending on the ambient temperature, a subject image signal to be formed into an image on the photoelectric conversion element
608
of the AF sensor IC changes in focal length and exhibits changes that depend on the temperature.
For this reason, appropriate distance measurement can be attained only when a subject image signal is sent to the microcomputer
607
, an ambient temperature outside the package
605
is detected by the thermometer
602
, and an image signal output from the photoelectric conversion element
608
is properly corrected by the microcomputer
607
.
The influence on the AF sensor IC
604
itself by ambient changes caused by changes in temperature of the AF sensor IC
604
itself must also be considered. The magnitude of dark current noise of the photoelectric conversion element
608
inside the AF sensor IC
604
influences the precision of the AF sensor IC
604
. As the temperature of the AF sensor IC
604
rises, the dark current noise increases at a predetermined ratio. The temperature of the AF sensor IC
604
is measured by the thermometer
603
on the package
605
, the value is sent to the microcomputer
607
together with a subject image signal, and dark current noise correction corresponding to the temperature value is performed for the image signal, thereby measuring the distance with high precision.
In the prior art, however, since the temperature of the AF sensor IC
604
is measured on the package
605
, the temperature of the AF sensor IC
604
itself cannot be accurately measured. The AF sensor IC
604
generally exhibits a temperature that is different from the temperature of the package
605
and an external temperature due to power consumption of the AF sensor IC
604
. More specifically, the temperature of the AF sensor IC
604
is higher than the respective temperatures of the package
605
and like elements due to heat generated from operation of the AF sensor IC
604
, and the heat dissipates via the package
605
or air. In other words, the temperature on the semiconductor substrate of the AF sensor IC
604
cannot be accurately measured by monitoring only the temperature of the package
605
and an external temperature.
Hence, to accurately correct dark current noise for the purpose of high-precision distance measurement, the temperature on the semiconductor substrate of the AF sensor IC
604
itself must be measured.
Also, the temperature of the package
605
itself is different from the external ambient temperature, and thus the thermometer
602
for ambient temperature measurement also must be employed. The thermometer
602
for ambient temperature measurement and the thermometer
603
for the AF sensor IC
604
must be separately adopted, which leads to a large number of components and high cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to downsize a photoelectric conversion apparatus for obtaining a high-precision image in spite of changes in temperature.
To achieve the above object, according to one aspect of the present invention, there is provided a semiconductor integrated circuit comprising on a single semiconductor substrate, photoelectric conversion means for photoelectrically converting an incident optical signal, a temperature dependent element which has a characteristic which exhibits a predetermined change in accordance with a change in temperature, and detection means for detecting temperature information of the temperature dependent element and temperature information received from outside of the semiconductor integrated circuit.
According to another aspect of the present invention, there is provided a photoelectric conversion apparatus comprising a semiconductor integrated circuit for photoelectrically converting an incident optical signal and including a first temperature dependent element having a characteristic which exhibits a predetermined change in accordance with a change in temperature and detection means for detecting temperature information, a device arranged outside the semiconductor integrated circuit, and at least one second temperature dependent element which is arranged inside the device and change in accordance with a change in temperature exhibits a predetermined temperature change, wherein the detection means detects temperature information of the first temperature dependent element and temperature information of the at least one second temperature dependent element.
The above and other objects, and features of the present invention will be apparent from the following description in conjunction with the accompanying drawings.
REFERENCES:
patent: 5412448 (1995-05-01), Kunishige
patent: 5914629 (1999-06-01), Maki
Canon Kabushiki Kaisha
Evans F. L.
Fitzpatrick ,Cella, Harper & Scinto
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