Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-05-03
2004-12-28
Porta, David (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S336100, C250S341100
Reexamination Certificate
active
06835932
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermal displacement element used for a thermal radiation detecting device such as a thermal infrared-ray detecting device etc, and to a radiation detecting device using the same element.
BACKGROUND ARTS
For example, an electrostatic capacitance type thermal infrared-ray detecting device and a light reading type thermal infrared-ray detecting device, have hitherto involved the use of a thermal displacement element including a base body (substrate) and a supported member supported on this base body (Japanese Patent Application Laid-Open No. 8-193888, U.S. Pat. No. 3,896,309, Japanese Patent Application Laid-Open No. 10-253447 and others). The supported member has an infrared-ray absorbing portion receiving and converting infrared-rays into heat, and a displacement portion thermally connected to the infrared-ray absorbing portion and displacing based on a bimetal principle with respect to the base body in accordance with the heat. Accordingly, the radiation is converted into heat, and the displacement portion is bent corresponding to the heat and thus displaces.
In the case of the light reading type thermal infrared-ray detecting device, for example, a reflection plate reflecting the received reading beam is fixed to the displacement portion of the thermal displacement element, the reflection plate is irradiated with the reading beam, and the displacement occurred in the displacement portion is read as a change in a reflecting angle of the reading beam, thereby detecting a quantity of the incident infrared-rays.
Further, in the case of the electrostatic capacitance type thermal infrared-ray detecting device, a movable electrode portion is fixed to the displacement portion of the thermal displacement element, a fixed electrode portion is fixed to the base body in a way that faces to this movable electrode portion, a change in height (an interval between the movable electrode portion and the fixed electrode portion) of the movable electrode portion due to the displacement occurred in the displacement portion, is read as an electrostatic capacitance between the two electrode portions, thereby detecting a quantity of the incident infrared-rays.
In the conventional thermal displacement element, however, the supported member supported on the base body simply has the displacement portion and the infrared-ray absorbing portion. Hence, as far as a temperature of the base body is not so controlled as to be strictly kept at a fixed level by use of a temperature controller such as a Peltier element etc, it follows that a quantity of the displacement of the displacement portion fluctuates when affected by an ambient temperature even if the quantity of the incident infrared-rays is the same. Accordingly, the infrared-ray detecting device using the conventional thermal displacement element is incapable of accurately detecting the infrared-rays from a target object unless the temperature of the substrate is strictly controlled. If the temperature of the substrate is strictly controlled, an accuracy of detecting the infrared-rays can be improved by reducing the influence of the ambient temperature, but nevertheless a cost inevitably increases.
Moreover, in the conventional thermal displacement element, the supported member supported on the substrate simply includes the displacement portion and the infrared-ray absorbing portion, and the displacement portion is composed of two layers having different expansion coefficients. Accordingly, the two layers composing the displacement portion are structured very thin in order to enhance a respondency by decreasing a thermal capacity and therefore bent upward or downward with respect to the substrate by dint of stresses (internal stresses) of the respective layers which are determined under the conditions when forming the layers, and it is in fact quite difficult to make the displacement portion parallel with the substrate in a case where the infrared-rays from the target object do not enter. Thus, according to the conventional thermal displacement element, the displacement portion is bent upward or downward with respect to the substrate in an initial state (i.e., initially) where the infrared-rays from the target object are not yet incident, so that a variety of inconveniences arise in the conventional infrared-ray detecting device using this thermal displacement element.
Namely, for instance, in the conventional light reading type infrared-ray detecting device, the reflection plate fixed to the displacement portion is initially inclined to the substrate. Therefore, alignments of optical elements of the reading optical system need a labor when assembled. Further, the supported portion and the reflection plate of the thermal displacement element are defined as one pixel, and these pixels are arrayed one-dimensionally or two-dimensionally on the substrate, wherein there is formed an image of the infrared-rays in relation to the reading beams. In this case, the reflection plate of each of the pixels is initially inclined to the substrate, and hence the respective reflection plates can not be positioned within the same plane on the whole, with the result that level differences occur stepwise between the respective reflection plates. Accordingly, for example; in a case where the image of the infrared-rays is obtained by forming images (that are images with light quantities of respective portions being different corresponding to inclinations of the corresponding reflection plates)of the respective reflection plates in relation to the reading beams, there arises such an inconvenience that the reading optical system for forming this image needs to have a large depth of field or the image formed becomes an image as if the original image is viewed obliquely.
Further, for example, in the conventional electrostatic capacitance type infrared-ray detecting device, the movable electrode portion fixed to the displacement portion is initially inclined to the fixed electrode portion. Since an electrostatic capacitance between the two electrode portions is in inverse proportion to an interval between the two electrode portions, the inter-electrode electrostatic capacitance becomes larger as the electrode-to-electrode interval is narrower, and there also increases a change in the inter-electrode electrostatic capacitance with respect to the change in temperature due to the irradiation of the infrared-rays. Namely, the infrared-rays can be detected with a higher sensitivity as the electrode-to-electrode interval is narrower. If the electrode portions are brought into contact with each other, however, a change causing a further increase in the inter electrode capacitance can not occur, and a dynamic range is restricted, so that the electrode portions must not be brought into contact with each other. It is therefore preferable that the interval between the electrode portions be set as narrow as possible enough not to make the electrode portions contact with each other. According to the conventional infrared-ray detecting device, however, the movable electrode portion is, as explained above, inclined to the fixed electrode portion, and consequently there arises an inconvenience in which the sensitivity of detecting the infrared-rays declines or the dynamic range is restricted because of the inter electrode interval being too wide or the electrode portions being brought into contact with each other.
It is an object of the present invention, which was devised under such circumstances, to provide a thermal displacement element and a radiation detecting device using the same element that are capable of obviating the variety of inconveniences hitherto occurred due to the initial flexure of the displacement portion.
It is another object of the present invention to provide a thermal displacement element and a radiation detecting device using the same element that are capable of restraining, if the strict temperature control is not conducted, an influence by a change in ambient temperature to a greater degree than in the prior art an
Ishizuya Tohru
Suzuki Junji
Miles & Stockbridge P.C.
Nikon Corporation
Porta David
Sung Christine
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