The invention relates to a vehicular lamp and, more particularly, to a structure for improving the appearance of the vehicular lamp. 
Generally, a vehicular lamp has a light source, a lamp body supporting the light source, and a translucent cover attached to the lamp body.  In a conventional vehicular lamp, the structural appearance of the lamp does not significantly change when it is on or off.  However, if a translucent cover (light cover) of a lamp has been half mirror-treated as disclosed in Japanese Utility Model Application Laid-Open No.  HEI 2-22505, the lamp interior is visible when the lamp is turned on.  When the lamp is off, the lamp interior is invisible because of the external light reflection of the translucent cover.  Thus, the appearance of the lamp changes when the lamp is switched on or off. 
However, since the translucent cover of the vehicular lamp described in the aforementioned Japanese application is only half mirror-treated, the translucent cover of the lamp when turned off shows a whitish reflection of a scene ahead of the lamp.  The reflection is similar to that of a widow pane attached with a half mirror film. 
The present invention provides structures of a vehicular lamp that is half mirror-treated.  That is, a vehicular lamp in accordance with the invention includes a light source and a translucent panel provided in front of the light source.  An upstanding wall portion extends substantially in a fore-aft direction to surround at least a portion of the translucent panel.  A plurality of quasi-reflector elements are formed in an inner surface of the upstanding wall portion.  At least a portion of the translucent panel is formed as a half mirror that has been half mirror-treated.  The half mirror portion is inclined at a predetermined angle with respect to the upstanding wall portion.  Thus, a reflection of the upstanding wall portion in the half mirror portion is observed when the lamp is turned off. 
As long as the translucent panel is provided in front of the light source, other members of the vehicular lamp are not limited in terms of specific configuration of the lamp body. 
The light source may be, for example, an incandescent bulb or an LED (light-emitting diode).  Furthermore, the number of the light sources may be more than one. 
As long as the translucent panel is provided in front of the light source, It may be an outer panel (translucent cover) exposed at a front face of the lamp or may be an inner panel provided rearwardly.  The translucent panel may be transparent and may have lens elements integrated therein. 
The specific construction of the upstanding wall portion is not particularly limited as long as the upstanding wall portion extends substantially in a fore-aft direction to surround at least a portion of the translucent panel.  The upstanding wall portion may be formed as an independent.  member or may be formed as a portion of a lamp body or a vehicle body-side member. 
The specific configuration of the quasi-reflector elements is not particularly limited as long as the elements are formed in the inner surface of the upstanding wall portion in a projections-and-depressions manner.  For example, the quasi-reflector elements may be cylindrical elements, fish-eye elements, or pyramidal elements, which extend in a fore-aft direction or a circumferential direction. 
The angle of inclination of the half mirror portion with respect to the upstanding wall portion and the position of formation thereof in the translucent panel are not particularly limited as long as the half mirror portion is formed so that when the half mirror portion is observed with the lamp turned off, a reflection of he upstanding wall portion is seen in the half mirror portion. 
As described above, in the vehicular lamp in accordance with the invention, at least a region in the translucent panel provided in front of the light source is formed as a half mirror portion that has been half mirror-treated.  Therefore, when the lamp is on, a lamp interior can be seen, and when the lamp is off, the lamp interior behind the half mirror portion cannot be seen because of the external light reflecting off the half mirror portion.  Thus, the visual appearance of the lamp is changed when the lamp is turned on or off. 
Furthermore, at least a portion surrounding the translucent panel is provided with the upstanding wall portion extending substantially in the fore-aft direction, and a plurality of quasi-reflector elements are formed in the inner surface of the upstanding wall portion, and the half mirror portion is inclined at a predetermined angle with respect to the upstanding wall portion so that a reflection of the upstanding wall portion is observed in the half mirror portion when the lamp is turned off.  Therefore, an image of the plurality of quasi-reflector elements formed in the inner surface of the upstanding wall portion can be reflected in the half mirror portion. 
Thus, according to the invention, the appearance of the lamp is improved in comparison with the conventional vehicular lamp, which when turned off shows a whitish reflection of a scene ahead of the translucent cover of the lamp. 
Color may be provided to the inner surface of the upstanding wall portion. 
The half mirror portion can be a curved plane so that the plurality of quasi-reflector elements formed in the inner surface of the upstanding wall portion can be shown distorted reflectively. 
Furthermore, the vehicular lamp may include a lamp body that supports the light source, and a translucent cover that is attached to the lamp body and that defines a lamp chamber together with the lamp body.  The translucent panel may be provided in the lamp chamber, and the upstanding wall portion may be formed as a portion of the translucent cover or the lamp body.  Therefore, the configuration of the translucent panel can be relatively freely set.  Furthermore, the positional precision of the upstanding wall portion can be enhanced.  Thus, the half mirror portion can substantially reflect light as intended. 
Furthermore, the lamp may include a reflector for forwardly reflecting light from the light source, and the reflector may have a plurality of reflector elements.  Therefore, when the lamp is on, the reflector elements can be seen.  Hence, it becomes possible to greatly change the appearance when the lamp is switched on or off. 
The reflector may be formed independently, or may be integrated into the lamp body or the like. 
Still further, if a region in the translucent panel in front of the light source is formed as an opening or is not half mirror-treated, the following operational advantages can be achieved. 
Since the half mirror portion partly reflects light incident thereon, the half mirror portion causes a fraction of the light emitted forwardly from the light source to be lost.  However, the region of the translucent panel contributes relatively little to the reflection of the upstanding wall portion.  Thus, if the region is formed as an opening or formed as a surface that is not half mirror-treated, the lamp can achieve a sufficient light luminosity while still substantially reflecting the upstanding wall portion. 
Furthermore, the appearance of the non-half mirror portion or the opening and the appearance of the other portion of the translucent panel are distinguished from each other when the lamp is off.  Therefore, the appearance of the lamp can be further enhanced. 
The translucent panel can be formed to extend in a substantially horizontal direction in a generally trapezoidal longitudinal sectional shape, and each of an upper portion and a lower portion of the translucent panel can be formed as the half mirror portion.  A central portion of the translucent panel in an up-down direction can be formed as the non-half mirror portion, and the central portion in the up-down direction can have a plurality of lens elements.  In this configuration, a lamp interior can be prevented from being clearly seen through the non-half mirror portion.  Furthermore, the lamp light distribution can be easily controlled. 
The plurality of lens elements may be formed either in an inner surface or an outer surface of the translucent panel.